Made a big mess with the SAK cli interface.
Merge branch 'master' into swiss_army_knife

Conflicts:
	pygrade/__init__.py
	pygrade/cli/task.py
Reworked CLI as swiss-army-knife style script with multiple subcommands.
Better name for CLI class. Added error checking and fixed bugs on CLI commands.
Unit attribute read/write. Fixed issue where tests were not passing config to loaded unit.