The README now shows all the common test environments that kgb supports.

Python unittest, pytest, and nose/nose2.
Examples have been updated to be more generic (less unittest-based) in

some cases, and to show how assertions work when using the mixin class,

the pytest fixture, or the standalone assertion methods.
The list of users have been fleshed out as well, showing some open

source projects I found that use kgb, and adding more of our own

products.
Installation instructions no longer recommend easy_install (even

though it still technically works).

Rendered the document. Tested the links. Checked the code samples for

obvious errors.