Make the version number PEP 440 compliant.
Merge remote-tracking branch 'origin/master' into fix/compliant-dev-versions
PR #214 feedback.

- Use `git describe` to get commit count and shorthash.
- Fail to import if setup.py hasn't been run
Drop the git hash from the full version.
Merge pull request #214 from enthought/fix/compliant-dev-versions

Make the version number PEP 440 compliant