update contributing documentation

Author: xalopp

CONTRIBUTING.md

@@ -0,0 +1,33 @@
+# Contributing
+
+## Setup
+
+We do recommend the following setup:
+
+* make sure that [Composer](https://getcomposer.org) is installed
+* clone the [PHP_CodeSniffer repository](https://github.com/squizlabs/PHP_CodeSniffer)
+* run `composer install` inside the `PHP_CodeSniffer` directory to install required dependencies
+* get the [Symfony Coding Standard](https://github.com/djoos/Symfony-coding-standard) and symlink, copy or move its `Symfony` subdirectory to `PHP_CodeSniffer/src/Standards/Symfony` 
+* symlink, copy or clone this repository to `PHP_CodeSniffer/src/Standards/MO4`
+
+        git clone https://github.com/squizlabs/PHP_CodeSniffer.git
+        cd PHP_CodeSniffer
+        composer install
+        cd src/Standards
+        git clone https://github.com/djoos/Symfony-coding-standard.git Symfony
+        mv Symfony/Symfony/* Symfony/
+        git clone https://github.com/mayflower/mo4-coding-standard.git MO4
+
+
+## Coding Standard and Tests
+
+If you contribute code, please make sure it conforms to the PHPCS coding standard and that the unit tests still pass.
+
+1. To check the coding standard, run in the repository root of `PHP_CodeSniffer`:
+
+        ./bin/phpcs --ignore='*/vendor/*' src/Standards/MO4
+
+2. The unit-tests are run from within the `PHP_CodeSniffer` directory
+
+        ./vendor/bin/phpunit --filter MO4
+

README.md

@@ -52,18 +52,7 @@ The MO4 Coding Standard is an extension of the [Symfony Coding Standard](http://
 
 ## Contributing
 
-If you contribute code to these sniffs, please make sure it conforms to the PHPCS coding standard and that the unit tests still pass.
-
-To check the coding standard, run in the repository root:
-
-        bin/phpcs --ignore='*/vendor/*'
-
-The unit-tests are run from within the PHP_CodeSniffer directory
-
-* clone the [CodeSniffer repository](https://github.com/squizlabs/PHP_CodeSniffer)
-* symlink, copy or clone the [Symfony Coding Standard](https://github.com/djoos/Symfony-coding-standard) and symlink, copy or move its `Symfony` subdirectory to `src/Standards/Symfony`
-* symlink, copy or clone this repository to `src/Standards/MO4`
-* from the CodeSniffer repository root run `phpunit --filter MO4`
+See [CONTRIBUTING.md](CONTRIBUTING.md) for information.
 
 ## Credit