Consider adding Inch documentation tool

[kowal]

http://trivelop.de/inch/

Please note that Inch "does not give you a grade for your whole codebase", just return grades for methods. It doesn't provide any way to automatically fail a inch command based on some metrics, however it can return JSON which polishgeeks-dev-tools can read and fail a rake tasks based on some values.

[kowal]

@nijikon @mensfeld what do you guys think about this one?

Inch represents tools which could just point out some areas to be improved (like documentation) without failing whole build. For examples it could parse inch stats command displaying grades distribution and use colors in output to show how "bad" it is.

Also it could not play along with yard coverage check, maybe those tools should be mutually exclusive.