Moved guard-test into a tools group.

This is according to its install guideline. These kind of stuffs really
messes up the namespace with all kinds of crap.

https://github.com/guard/guard-test#install
Dissolve the merged test/development groups.

A development and a test environment are not the same and they should
not share gems by default. Add gems accordingly.
Merge pull request #25 from badeball/gemfile-cleanup

Gemfile cleanup: 
I checked it out and had no problems running guard after this cleanup.