- Status bar blame information will hide
  - CodeLens change to a `Cannot determine...` message and become unclickable
  - Many menu choices and commands will hide
Fixes #36 - Blame information is invalid when a file has unsaved changes
Fixed #38 - Toggle Blame Annotation button shows even when it isn't valid
Preps v2.9.0

Also gracefully deals with the times when git isn't in the PATH

Removes typings (using npm instead)
Fixes some promise catches