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.
Removed some dead commented code and unused imports.
Added -notify.
Fixed some bugs.
Refactoring.
Readme tweak.
Added a bit of javadoc.
Change some print statements.
Merge branch 'master' into tomk-hadoop
Fix usage whitespace.
Add help.