mars stuff
Clean up mars code
Add GCV function
Restructure
Add backward pass to mars
Clean up code
Add new data and format correctly
Implement gradient boosting decision trees
Begin coding decision tree implementation
Partition data
Clean up code
Implement decision trees
Fix decision tree implementation
Clean up gen_data
Add documentation
Rename data files
Remove tree coefficients from GBDT
Merge branch 'gbdt'

Conflicts:
	predict.m
	regress.m
	train.m