Option to remove colors like mocha's --no-color

Most of mocha's reporters use color escape codes in them, and in node-based Mocha it detects if the terminal supports it, but in phantomjs it cannot, and color codes are always on. This is much needed for things like build logs and hindered consoles like Sublime Text 2's and Windows' cmd.exe.

I've created a new reporter, `Bw`, that strips out the escape codes, but this isn't the proper fix. Probably an exposed command line option that the `Reporter` class can take in and pass to mocha?

Thoughts?