Fix irb invocation example in CONTRIBUTING.md

* Use `bundle console` to load "fauxhai" automatically
* Fix quotes
Add RedHat 5.9
Merge pull request #73 from bytheway/redhat-5.9

Add RedHat 5.9
Merge pull request #72 from tmatilai/contrib-irb

Fix irb invocation example in CONTRIBUTING.md
Add Redhat 5.10
Add RedHat 6.0
Add RedHat 6.1
Merge pull request #76 from bytheway/redhat-6.1

Add RedHat 6.1
Merge pull request #75 from bytheway/redhat-6.0

Add RedHat 6.0
Merge pull request #74 from bytheway/redhat-5.10

Add Redhat 5.10