Rename *Helper file to something else

NewChunkHelper ==> ChunkSplitter
Missing rangecheck in sparse-double-chunk compression
HEX-1695: Update h2o.gbm() to have imbalanced data handling, incl. docs.
Merge branch 'master' of https://github.com/0xdata/h2o
Rename some H2O R logging methods. Add several checks to ensure directory that logs are saved to exists before attempting to write file.
Automatically create 75%/25% splits for all (original and rebalanced) frames in LoadDatasets.java
Merge branch 'master' of https://github.com/0xdata/h2o
Fix usage of FrameSplitPage in LoadDatasets.java, exposes an assertion error.
Fix PUB-661: make CM consistent between GBM/DRF/GLM2 and AUC.
handle bad rows properly
PUB-511: Add tutorial for GBM
PUB-602: Update Random Forest tutorial to FVec.
PUB-602: Update DeepLearning tutorial to FVec.
PUB-602: Update GLM tutorial to FVec.
Merge branch 'master' of https://github.com/0xdata/h2o
light cleanup of speedrf html
fix config file
always increment the test_run_id by 1 for internal use, even on test fail
Avoid NPE.
maintenance on tests -- use col index if cannot come up with a good colname