Added a notification if you try and use local charm upload when your Juju version does not support it.
Merge pull request #105 from hatched/local-charm-not-supported

__To QA__
- Downgrade your version of Juju to 1.16.x version.
- Deploy the ~juju-gui latest charm.
- Set juju-gui-source to this branch.
- Try and deploy a zip archive of a charm and a notification should show.