Cleanup Vec enum
better messaging on test_rf_predict.py error
use full covtype.data for test_rfview_score training -> model. Bigger model for the subsequent predict to use
oops. typos. fixed.
MRTask2.invoke renamed .doAll
Minor miscounting in new C1xChunks
Remove empty file?
More distributed tree-building

Split out Tree from GBM.  Make it distributable, and a cleaner
abstraction.  Use the new Tree API in GBM.  Rename MRTask2.invoke to
doall.  Convert more GBM code to fluid-vec style.
New split-out distributable tree
Fix test for new C1NChunk compression
Merge branch 'master' of https://github.com/0xdata/h2o
some tests for looking at RFview and GeneratePredictionsPage with covtype20x, especially breaking out RFView as 'scoring' separately on an uncached key.
Merge branch 'master' of github.com:0xdata/h2o
make a unique key for the predict also (to get uncached times)
Added MapperToDriver messaging.
Added EmbeddedH2OConfig concept.
Changed a bunch of places where System.exit() was called into H2O.exit().
Added a few notify calls to the embedded h2o config at strategic places.
Bug w/C2SChunk not having correct bias
Implement C2Chunk inflation
Correct length of C1 & C1NChunk
Implement C2SChunk set8
Removed some dead commented code and unused imports.
Actually build & run distributed trees.

Last non-distributed data pass gets distributed.
Histograms get a 'reduce' and do proper array alloc in the map call.
Run & fix a few bugs with prior MRTask2 passes.
Compute regression (squared error) & classification errors.
Turn off some debug printing.  Clean up treeMin/treeMax.
Remove unneeded (leaked) arrays as tree building progresses.