working through by() 'step' in GraphTraversal and its effects on order, select, groupCount, aggregate, etc.
Add Io interface #376

Removed hacked on methods in GraphProvider that used to return GremlinKryo and GraphSON related stuff from the implementer.  Now that Io is a first class citizen the tests can be much more direct in what they do.
orderBy no longer exists. Now its order().by() and works for both element and object ordering. Refs #413.
aggregate().by() is now available. Refs #413.
path(), store(), and dedup() are now by()-enabled. Refs #413.
minor nothing.
Merge branch 'master' into by_step
Property getters return empty if the key is the partition key in PartitionStrategy.
tree(), group(), and GraphTraversal.by() all updated. This is very very clean and pretty. Such a good idea. Fixed #413.
Merge branch 'by_step'
updated documentation with new by()-work.
added better parameter names to by() in GraphTraversal.
doc updates.
doc updates.
updated CHANGELOG.
renamed random() to coin() and added sample()-step which supports random walks. Fixed #416.
fix in CHANGELOG.
fix in CHANGELOG.
Minor profile cleanup
1024M for Hadoop testing. May not be enough still. Need to figure out how to make a new JVM for each @Test.