Command line

Mostly grader_spec for Grader.cli()
* Started delegating to hw3_grader and kin. See comment, diffs on commit 6cdf59 for old, simpler switch statement.
* Stubbed need for any physical resources, leaving integration to cuke tests.
* Fix for feature_grader.feature and subject_code_steps file is in this branch. I can extract it if desired.