More user/shell agnostic path configuration

A 'configure_appengine' program is provided to auto configure app engine
paths. Usage is:

    vagrant ssh
    configure_appengine
    source <your shell config file, ex: bashrc, zshrc>

You need to run the above just once (I'm looking forward to improve that
because it's really less than optimal) or anytime you change your
default shell.
Merge pull request #2 from ikame/master

More user/shell agnostic path configuration