minor bug fix in docs.
Remove todo.
Add changes from @MMcM to make sure Kryo reads the Vertex Property Ids. #252

Also, corrected the DetachedVertexTest.shouldNotEvaluateToEqualDifferentId test to read and detach the vertex first before adding the new "marko" vertex.  That seems to solve the uniqueness problem.
Properly read vertex properties from GraphSON with readGraph.

Prior to this change it was ignoring vertex properties!  Not sure how there wasn't a test for this.  Seems like we still have holes in IO.
Update changelog.
more documentation on Gremlin OLAP. Stubbed SortedTraverserMapReduce. Renamed TraversalResultMapReduce to TraverserMapReduce. Ref #272.