Improve performance by loading dependencies only when needed.

[nikhilkh]

Some of the node modules that index.js depends on do not need to be loaded, unless a later version of an npm module is found. Delay loading them provides better startup performance by pay-for-play. Here's the simple test that I performed on warm-startup and it improve the node module load time by 50% for update-notifier and it's children.

I will shortly submit a PR with my change.

--- a/before.txt
+++ b/after.txt
@@ -1,36 +1,18 @@
->> Module load abbrev parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 2
-> Module load nopt parent: . : 7
+> Module load nopt parent: . : 3
 > Module load underscore parent: . : 5
->> Module load child_process parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 2
->>>> Module load ./polyfills.js parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/index.js : 2
->>> Module load graceful-fs parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 7
->>> Module load osenv parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 3
+>> Module load child_process parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 3
+>>>>> Module load ./fs.js parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/node_modules/graceful-fs/graceful-fs.js : 2
+>>>> Module load ./polyfills.js parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/index.js : 3
+>>> Module load graceful-fs parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 9
+>>> Module load osenv parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 4
+>>> Module load object-assign parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 2
 >>>>> Module load crypto parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/node_modules/uuid/uuid.js : 4
 >>>> Module load ./rng parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/index.js : 5
 >>> Module load uuid parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 7
 >>> Module load xdg-basedir parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 2
->>>> Module load slide parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/index.js : 2
->>> Module load write-file-atomic parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 4
->> Module load configstore parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 28
->> Module load chalk parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 5
->>> Module load semver parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 2
->> Module load semver-diff parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 3
->>>>> Module load http parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 3
->>>>> Module load https parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 3
->>>>>> Module load stream parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/node_modules/got/index.js : 2
->>>>>> Module load ./lib/_stream_readable.js parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/node_modules/got/index.js : 5
->>>>>> Module load ./lib/_stream_writable.js parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/node_modules/got/index.js : 2
->>>>> Module load readable-stream parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 11
->>>>> Module load url-parse-lax parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 2
->>>>>> Module load ./vendor/parse parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/node_modules/got/index.js : 2
->>>>> Module load parse-json parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 3
->>>>> Module load ./package.json parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 2
->>>> Module load got parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/index.js : 37
->>>>> Module load ./lib/utils parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/node_modules/package-json/index.js : 2
->>>> Module load rc parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/latest-version/index.js : 4
->>> Module load package-json parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 42
->> Module load latest-version parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 43
->>> Module load string-width parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 4
->> Module load boxen parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 9
-> Module load update-notifier parent: . : 92
+>>>> Module load slide parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/node_modules/configstore/index.js : 3
+>>> Module load write-file-atomic parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 6
+>>> Module load dot-prop parent: /Users/nikhil/Developer/cordova/cordova-cli/node_modules/update-notifier/index.js : 3
+>> Module load configstore parent: /Users/nikhil/Developer/cordova/cordova-cli/src/cli.js : 35
+> Module load update-notifier parent: . : 40

[sindresorhus]

Was fixed by #82.