Added a bootstrap command

This new command builds all the wheels needed to install curd, and prints a list of those wheels. That way, they are ready for install in a new virtualenv.

This way, one can run `pip install $(curd bootstrap)` in a fresh virtualenv and have curd installed much faster than pip alone would have (30s vs 5s for me). This command could even be made a virtualenvwrapper init script, since it's quite fast.