Updated Composer usage instructions

- Reference Composer's install docs
- Use a globally installed Composer (the result of Composer's docs)
- Don't specify version, `composer require` automatically requires the latest version (and 1.0.* was quite outdated)

CONTRIBUTING.md

@@ -18,12 +18,11 @@ To install the project and run the tests, you need to clone it first:
 $ git clone git://github.com/Ocramius/ProxyManager.git
 ```
 
-You will then need to run a composer installation:
+Make sure you've [installed Composer](https://getcomposer.org/download/) and install the dependencies:
 
 ```sh
 $ cd ProxyManager
-$ curl -s https://getcomposer.org/installer | php
-$ php composer.phar update
+$ composer update
 ```
 
 ## Testing
@@ -35,4 +34,3 @@ $ ./vendor/bin/phpunit
 ```
 
 Accepted coverage for new contributions is 80%. Any contribution not satisfying this requirement won't be merged.
-

docs/download.md

@@ -1,11 +1,7 @@
----
-title: Download / Installation
----
-
 ## Download / Installation
 
-The suggested installation method is via [composer](https://getcomposer.org/).
+The suggested installation method is via [Composer](https://getcomposer.org/):
 
 ```sh
-php composer.phar require ocramius/proxy-manager:1.0.*
+composer require ocramius/proxy-manager
 ```