Added CONTRIBUTING file

Author: shazron

CONTRIBUTING.md

@@ -0,0 +1,29 @@
+## Contributing to ios-sim
+
+Github url: 
+
+        https://github.com/phonegap/ios-sim
+
+Git clone url: 
+
+        https://github.com/phonegap/ios-sim.git
+
+## Filing an issue
+
+Please run the commands below in your Terminal.app and include it in the issue:
+
+```
+1. sw_vers -productVersion
+2. ios-sim --version
+3. xcodebuild -version
+4. xcode-select --print-path
+5. gcc --version
+```
+Also include **command line arguments** you used for ios-sim.
+
+
+## Sending a Pull Request
+
+Please **create a topic branch** for your issue before submitting your pull request. You will be asked to re-submit if your pull request contains unrelated commits.
+
+Please elaborate regarding the problem the pull request is supposed to solve, and perhaps also link to any relevant issues the pull request is trying to fix.