Fix import errors with unicode filenames
Add tests for imports with unicode filenames
Fix unicode errors on exceptions and logging
Use upside-down english for unicode text
Remove unnecessary encode
Bump diff-cover version
Cleaner tests
Utility functions for finding courses by id
Add unicode handling to the signing and verifying logic
Merge pull request #1050 from edx/hotfix/2013-09-19

Hotfix/2013 09 19