Update changelog to be v2 API docs sites compatible:
Update changelog to be v2 API docs sites compatible:

- First, not sure why a lot of spurious single-backtick
  names were not causing issues for v1 CI...maybe I never
  added warnings-to-errors Sphinx building to its travis.yml?
- All ref, doc, implicit API links changed to monospace
  formatting.
- Some links turned into regular formatting.
- Other related tweaks to prevent Sphinx errors.

fabric/fabric