add waffle.io badge
Merge pull request #16 from waffleio/master

waffle.io Badge
Merge commit '2e1005021fd28faf719155d18000065dac160bd7'

* commit '2e1005021fd28faf719155d18000065dac160bd7':
  add waffle.io badge
Merge branch 'master' into sass-singularity

* master:
  add waffle.io badge