NOJIRA - Gemfile - use single quotes - (non priority)

Since rubygems is now suggesting to use single quotes, we should be consistent and do the same

e.g. https://rubygems.org/gems/angular-gem
http://cl.ly/Wv9C
Merge pull request #2767 from christianv/nojire-gemfile-quotes

NOJIRA - Gemfile - use single quotes - (non priority)