add a pip-update command

[Jaymon]

lots of times I want to update a module from github, and everytime I have to look up the syntax and copy paste, what I would love is a small script that will find the current module in python's site packages (or the virtual env) and load its setup.py and get the url and current version, if it is a github url it will make this request:

pip install git+https://github.com/NAME/PROJECT#egg=NAME>CURRENT_VERSION

so instead of having to look up the url (which I just had to again by the way) I could just do:

pip-update NAME

and have it do all the heavy lifting.