fix libav build
Demonstrate that circular references aren't collected.
Stream and Codec hold onto ContextProxy

This never forms circular references.
Starting the great reorganization

Imports were not fixed, or fixed really badly.
The great reorg takes another turn
Fix a lot of imports

Only tested with examples/decode.py
Use err_check
LibError extends RuntimeError; shuffle imports
AVError extends EnvironmentError; start testing

This is much more like IOError or OSError.
Setup Travis to run actual tests
Fix the docs
The package name is "nose", not "nosetests"
Testing with Vagrant
Refining Vagrant tests
Add LD_LIBRARY_PATH to Travis
Slightly more automatic Vagrant setup
VideoFrame format tweaks

f.pix_fmt -> f.format
f.to_rgba() -> f.to_rgb()
Docs should include all members
Notes and test framework
Add weak ref of Context to Stream

Then it can start encoding. There must be a nicer
way to do this...