doc: use cargo new instead of mkdir and cargo init

This is slightly simpler.

PR #166

Author: tshepang

README.md

@@ -61,9 +61,8 @@ it.
 First, create the project in a new directory:
 
 ```text
-$ mkdir jiff-example
+$ cargo new jiff-example
 $ cd jiff-example
-$ cargo init
 ```
 
 Second, add a dependency on `jiff`:

src/lib.rs

@@ -145,9 +145,8 @@ it.
 First, create the project in a new directory:
 
 ```text
-$ mkdir jiff-example
+$ cargo new jiff-example
 $ cd jiff-example
-$ cargo init
 ```
 
 Second, add a dependency on `jiff`: