Updates CONTRIBUTING docs sort bug in fedora 20

Informs contributors that check for requirements style
can fail due to sort bug in fedora 20 -
https://bugzilla.redhat.com/show_bug.cgi?id=1055597

Change-Id: I24c73c74c37547e9ee5316bb53e9a5eb6cf2e393
Merge "Updates CONTRIBUTING docs sort bug in fedora 20"