Boss executable

Yesterday while writing a [Homebrew](http://mxcl.github.io/homebrew/) formula for Chicago Boss that would install CB into /usr/local, I realized there was no real "boss" command that could be run easily from anywhere to create a new app or manage the app in the current working directory. So I wrote one.

This commit allows devs to do things like "boss new APP" or "boss start", just like a developer would do with the "rails" command. Because the boss command follows symlinks, it works well both right after a download (just like using "make app project=FOO" or in the context of a Homebrew installation on the user's path.