Allow updating of hashes from pip freeze

[cwood]

I want to be able to do a shortcut over a package and have it update to the latest version in the current app.

E.g; django in requirments is 1.3.1 but we upgrade to 1.4.5. Pressing a key combo should update it in requirements.

I am thinking since that will increment it up to the next version.

If its a editable package it should update the url/hash used in the name of the egg