Moved Graph -> DirectedGraph
Fixed type bug
Added Graph abstract class and UndirectedGraph class. Everything compiles but the existing tests fail and more tests are needed.
Added failing tests for addNodeCheck
Removed blank unit tests and temporarily undid an attempt to factor out common code for addNode - it would require a bit more thought.
Added tests for UndirectedGraph class and removed code from UndirectedGraph
Added code and fixed test for UndirectedGraph, and removed unnecessary catching of exceptions
Rewrote TestDirectedGraph to use Hamcrest's hasItem(s) instead of instantiating ArrayLists with which to compare the values