Fix help message for Cluster's --features argument

The Cluster app's help message for the --features argument was
previously printing out the possible values for distance functions
rather than the possible values for features.
Merge pull request #10 from njwilson/fix-features-help

Fix help message for Cluster's --features argument
Added files for checking HW2.
Increase version to 0.3.0
Add stub files for HW4.
Update README, prepare for 0.3.0 release.
Merge remote-tracking branch 'upstream/master'