Update short project description (creds to @briandoll)

README.md

@@ -1,7 +1,7 @@
 Composer - Dependency Management for PHP
 ========================================
 
-Composer is a dependency manager tracking local dependencies of your projects and libraries.
+Composer helps you declare, manage and install dependencies of PHP projects, ensuring you have the right stack everywhere.
 
 See [https://getcomposer.org/](https://getcomposer.org/) for more information and documentation.
 

composer.json

@@ -1,6 +1,6 @@
 {
     "name": "composer/composer",
-    "description": "Dependency Manager",
+    "description": "Composer helps you declare, manage and install dependencies of PHP projects, ensuring you have the right stack everywhere.",
     "keywords": ["package", "dependency", "autoload"],
     "homepage": "http://getcomposer.org/",
     "type": "library",