Update for pyannote.audio 2.0

[hbredin]

Before we make this repo public, it needs to be updated to match the API of pyannote.audio 2.0.

It has not been released yet but there won't be a lot of changes in develop branch before the release (at least in terms of user-facing API).

The updated speech activity detection tutorial is a good place to get the idea of what changes. The main difference is that pyannote-speech-detection is now pyannote-audio sad.