Add metric_fu into the development dependencies

Hopefully, to give some insight to part of the code base which can be
simplified. I think that this will be nice to have in addition to
something like CodeClimate because it will work without depending up
an external service.
Add version and code quality badges

Includes:
* Code Climate, for analyzing code quality
* Gemnasium, for analyzing in dependencies
* Badge Fury, for showing the current packaged version of the gem
Merge pull request #56 from acant/feature/metrics

Add metric_fu and some badges to the README