Peer review feedback

[agitter]

@qualiaMachine reviewed the workshop materials and had the following suggestions.

a. Found a typo here: "It is easy to go to deep in the tree" should be "too" instead of "to"
b. A graphic or two showing ROC and Precision recall curves under the Error Curves section here could be helpful
c. Maybe add snippet paragraph about recall here since both precision and recall tend to be popular measurements
d. Maybe define regularization before talking about L1 and L2 hyperparameters (under Step 2 Train Classifier here)

Thanks for the help @qualiaMachine