Add some extra mapper, for standardization and convenience.

Hi, thank you for you maintenance ruby-test-mode, I heavy use this mode for fast switch between code and test,
I spend hours finish and test all map, just for easy to use and create test file consistency, and Fix all error I known. it worked fine for me, not only for rails, but for normal ruby code.

I had changed other place for support new file extension, maybe I change is wrong, so just have a look if you
have time. anyway, it worked fine for me.