Mux-python

* Updates docs for encoding_tier
* Adds `generated_vod` to `text_source` enum
* Pin Python version to ensure we can package for now

New release to make publish work

Fix to remove egg files before upload

General:

Assorted documentation improvements
Added MIT license to setup.py
Mux Video:

Added Multi-track Audio
Added 4K & max_resolution_tier
Added Encoding tiers
Added Generated captions (beta)
Deprecated max_stored_resolution, replaced with resolution_tier
Mux Data:

Added Video startup failure
Added Monitoring breakdown timeseries

This release adds parameters to the response of some of the API calls (to better match our implementation), and improves the unit test for exercising the signing key routes. This release also includes a few documentation updates as well.

This release adds the ability to report delivered seconds by resolution, in support of the new resolution-based pricing. It also adds the `crop` layout to Spaces broadcasts.