[TAV-442] Add licence declaration to the gemspec.
[TAV-443] Ensure correct files are in the gem.

Use 'git ls-files' for this...
Specify the lib dir in the gemspec.

Not sure this is needed anymore, but better to be safe than sorry.
[TAV-439] Set finished time for failed/cancelled runs.

Helps in UIs, etc.
[TAV-444] Add a cancelling state to a run.

This prevents race conditions while cancelling - specifically ghost interactions
appearing after hitting cancel.