working through by() 'step' in GraphTraversal and its effects on order, select, groupCount, aggregate, etc.
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
tree(), group(), and GraphTraversal.by() all updated. This is very very clean and pretty. Such a good idea. Fixed #413.
Merge branch 'by_step'