Fixes issue #1
Compare target to mentions case-insensitively.
Mention names not case sensitive.
Revert "Fixes issue #1"

This reverts commit 08d08285892c880d77e434c39fd306f6694145cb.
Fixes issue #1
Allow people to give themselves bad karma.
Fixes issue #2
Mention names should be compared case-insensitively because that's how HipChat does it.
Changed 'negative' and 'positive' to 'good' and 'bad' in help message.
Closes #3 by adding 'explain' behavior