add comments to minds
fix routes problem
Merge branch 'master' into comments

Conflicts:
	app/controllers/minds_controller.rb
add comments' factory
isolated and refactored comment model tests by using factory
routing tests for comments controller
MD-20 tests
added case when mind does not exists
MD-19 tests and checking for persistence and errors of invalid objects
MD-19 tests and checking for persistence and errors of invalid objects