Delete Gemfile.lock (#11)

* Delete Gemfile.lock

File was added as part of the fix to the logger but according to [Yehuda Katz](https://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/) this was a mistake:

> When developing a gem, use the gemspec method in your Gemfile to avoid duplication. In general, a gem's Gemfile should contain the Rubygems source and a single gemspec line. Do not check your Gemfile.lock into version control, since it enforces precision that does not exist in the gem command, which is used to install gems in practice. Even if the precision could be enforced, you wouldn't want it, since it would prevent people from using your library with versions of its dependencies that are different from the ones you used to develop the gem.

> When developing an app, check in your Gemfile.lock, since you will use the bundler tool across all machines, and the precision enforced by bundler is extremely desirable for applications.

https://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/

* Add Gemfile.lock to the files ignored by git

For a library this file is better if it is not included ever:

> Do not check your Gemfile.lock into version control, since it enforces precision that does not exist in the gem command, which is used to install gems in practice. Even if the precision could be enforced, you wouldn't want it, since it would prevent people from using your library with versions of its dependencies that are different from the ones you used to develop the gem.

https://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/

.gitignore

@@ -9,4 +9,5 @@
 vendor
 test/examples/hello-world-docker/pkg
 *.iml
-.DS_Store
+.DS_Store
+Gemfile.lock