Fix RTD build (#81)

GHA fixes (#69)

fixed version checking code

build cleanup

- caching
- adop stages
- auto-release on tag
- switched to hacking linting

travis: enable build of release tags

Allow travis to trigger builds for tags in order to release them.

Change-Id: I351c4406032d44f3dc77d83995ca988462ed1c05

Version 0.2.8

Version 0.2.6