Split AudioFifo into its own module
Rename some audio attributes
AudioStream uses AudioFrame as buffer
Calculate AudioFrame buffer size on decoded frames
Start AudioFormat
Start AudioLayout
Decoded VideoFrames construct a VideoFormat
WIP adapting AudioFrame to use new format/layout

This breaks audio even more, for now.
Split Codec into VideoCodec and AudioCodec
Remove dummy streams
Simplify AudioFrame buffer allocation
Codecs use format and layout objects
Abstract Plane from VideoPlane
Properly calculate AudioPlane buffer_size
Decode example PLAYS AUDIO (assuming s16le)
Docs, notes, and disable AudioFifo properties
Merge branch 'audio' into develop
Adjust __repr__ to show no submodules
Import many of the things into `av`
Pull in doctests