Issue #2 fix, plus Beth Ashinsky's Linear Regression code

Sorry for the massive Pull Request. This includes the test code written by Simon Li that exposes Issue #2, the fix for Issue #2, as well as the latest Linear Regression code additions to FeatureSet.py used by Beth Ashinsky. The two development branches I had working on Simon and Beth's stuff got intermingled, and I was too lazy to unmingle them.