Distribute as a wheel

[atagar]

Migrated from ticket 20500.

At PyCon sounded like wheels (*.whl) are the new hotness when it comes to distributing python modules.

Don't think we want to jump on this right away for a few reasons...

1. Still pretty new. They haven't even reached their 1.x release yet.
2. Really all we care about is built-in pip support. Not clear all versions support wheels.
3. Requires setuptools. It's kinda nice just needing the builtins.
4. We don't need any of the capabilities wheel provides. Stem is a simple module without any native components.

That said, if this becomes the standard then once it's universally supported we should obviously swap.