Groups for simplecov report

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.
Better Rubymine compatibility for .simplecov

Rubymine's code coverage tools separate collection from reporting so
that multiple runs can have their data merged.  To separate, collecting
from reporting, SimpleCov.start is only run when not using Rubymine (as
indicated by a lack of the RM_INFO environment variable).  This way,
`rake spec` will collect coverage info and generate the report as
before, but Rubymine will only collect coverage when using 'Run ... with
coverage enabled' button and will only generate a report when using
'Generate Coverage Report' as is the intended behavior in Rubymine.
Merge remote-tracking branch 'rapid7/feature/simplecov-groups' into rapid7
Merge branch 'master' of github.com:rapid7/metasploit-framework into rapid7