WIP - testing
PUB-768 - corrected response which is used for cross validation scoring.
PUB-768 fixing memory leaks

There were several memory leaks:
 - scoring results for individual validation folds were not deleted
 - scoring result for train data was not delete
 - SharedTreeModelBuilder in the context of cross validation forget to
   delete transformed response (since the builders called DRF/GBM.clone())

Minor cosmetics changes.
PUB-768 shared test for Tree Builders which tests workflow
with balance and cross-validation on binomial/multinomial
data with integer/enum response columns.

This is a generic testing strategy which individual tree builders
should override.
PUB-768 DRF tests for imbalance data with cross validation.

Minor cosmetics changes in imports.
PUB-768 GBM tests for imbalance data with cross validation
Updated all tests suite and included all tests.
PUB-768 SpeeDRF tests for imbalance data with cross validation
SpeeDRF test for balancing and cross-validation
Disable SpeeDRF tests since
 - SpeeDRF does not support handling different categoricals in
   train/test dataset
 - leaking keys
Removed abstract test from runner.
Merge branch 'master' of github.com:0xdata/h2o
Merge branch 'master' of github.com:0xdata/h2o
Merge branch 'master' of github.com:0xdata/h2o
Force PST timezone in ParseTimeTest test.
Merge branch 'master' of github.com:0xdata/h2o