SimpleCov Groups and better Rubymine compatibility

Add Changed group that will show the coverage for any untracked, unstaged, or staged file so developers can more easily see if that their changes are covered.

Other groups added for different libraries under lib.

For Rubymine compatibility, make coverage collection controllable using Rubymine and reporting only occur when requests. Coverage collection and reporting remains unaffected when running `rake spec` from outside Rubymine as Rubymine is detected using the RM_INFO environment variable.