'extension-looking' file names are changed incorrectly.

I like to name my files like `base.model.coffee`. However, this plugin currently blasts away `.model.coffee` for the `dest` property of a file in the `this.files` array. This is due to grunt's regular expression. For grunt, this is correct, but  causes problems when compiling to coffeescript as explained above.

This pull request overwrites the `dest` property by replacing the 3 possible coffeescript extensions with `.js` and swap places it at the end of the `dest` path instead of what grunt produces.

I've also renamed the `.md` file to something different for clarity in tests.