Changelog does not update when using sphinx-autobuild

[maxnoe]

To reproduce:

1. Add changelog file in the configured place, e.g. docs/changes/123.feature.rst

2. Run

   $ sphinx-autobuild docs docs/build/html
   

3. Open page in browser.

4. Edit changelog file

5. Page reloads but changelog is still the previous version.

[Cadair]

Presumably this is because sphinx is caching the rst file with the directive in and not re-running the directive as the file hasn't changed. I am not sure if there is a way to kill off the cache to trigger a re-evaluation.

[maxnoe]

Fix in #29