[added] support for mocha `grep` option

@mantoni Love your work.  I regularly use the grep option, added support here.
My projects stick with [SemVer](http://semver.org) and this is a new feature with an API addition. The version number will be `1.1.0` so that Mochify can explicitly depend on it.
Also: I'd prefer to compile the changes when I actually make the release, so that I can mention colaborators ;-)