add additional sklearn parameters

[falkben]

The following is a list of parameters that sklearn random forest has that we do not.

• [ ] criterion (gini/entropy)
• [ ] min_samples_leaf: The minimum number of samples required to be at a leaf node.
• [ ] min_weight_fraction_leaf
• [ ] max_leaf_nodes
• [ ] min_impurity_decrease
• [ ] bootstrap
• [x] oob_score
• [ ] verbose
• [ ] warm_start
• [ ] class_weight

Some of these may be of interest to support. Some are relatively easy to add.

[bkj]

I'm trying to run some larger-scale hyperparameter tuning experiments --warm_start would be particularly useful.

A verbose flag would also be very nice to keep logs clean.