Triage issues for v0.4.0

There has been a ton of work done since v0.3.3. We should cut out a new release.

However, I get the feeling that there are some regressions with it. We should triage the tickets still open since v0.3.3 to make sure they can be "ignored" for a new release.

(edited to just be the issues left to address)

• Assert no blocking issues on GitHub:
  • #202 (closed)
  • #212 (closed)
  • #257 (closed)
• Document everything backwards incompatible in changelog:
  • Stream.encode returns a list of packets, instead of a single packet.
  • AudioFifo and AudioResampler will raise ValueError if input frames inconsistant pts.
  • CodecContext.rate has been removed, but proxied to VideoCodecContext.framerate and AudioCodecContext.sample_rate. The definition is effectively inverted from the old one (i.e. for 24fps it used to be 1/24 and is now 24/1).
  • Fractions (e.g. time_base, rate) will be None if they are invalid.
  • InputContainer.seek and Stream.seek will raise TypeError if given a float, when previously they converted it from seconds.

😨