Drop "transaction isolation" related feature/tests for now #31

Reconsider them for the future after GA.  It's hard to make this happen without more concrete implementations in place to help standardize functionality.
Fixed #90 ... changed given() to where() and allows Traversal to be used as the predicate between one or two variables in the Map<String,Object> -- collaborated with @joshsh on this. Added respective WhereTest cases and propagated requisite changes to gremlin-neo4j and Neo4jTraversal/Vertex/Edge.
Changed the GraphFactory.open() method to take an arbitrary set of strategies to apply #91
Correct docs with respect to the GraphFactory.open() api.
fixed the age-old aggregator bug in Giraph. Wow. That was soooo painful -- 3 days of debugging. What is nice is that the GraphComputerTest is way more sup'd up to the point of finding bugs in TinkerGraphComputer. GraphComputer is coming along.
an extra assert() for safety sake.
better warning message if GIRAPH_GREMLIN_LIBS is not set. Also, optimizations where a BSP round is not needed if memory does not need to be calculated.
Added a public MatchStep.addTraversal()
Merge branch 'master' of github.com:tinkerpop/tinkerpop3
added MatchWhereStrategy that folds where() traversal clauses into match(). Added one test case around predicate traversals to verify it. Added Step.reset() to allow for reseting a step. Added Traversal.rest() to allow reseting of a traversal. Updated some of the <E2> types in Vertex and Edge as the E2 is known in such situations.
minor tweak.
more thoughts on MatchWhereStrategy...for @joshsh.
Add close() as a GraphStrategy.
more MatchTest tests -- finding more failings @joshsh.
Graph instances defined or re-bound by an init script in Gremlin Server gets its reference written back to the global space #91

The by-product of this is that graph strategies can now be configured via init script in gremlin server.
Added a GiraphComputerTest that ensures proper derivation of memmory (Giraph specific). Fixed a minor bug in Memory.asMap(). Added docs around the where()-clause for match().