Preliminary tests for our DFS iterator.
Preliminary path-finding DFS iterator.
Modified path finding DFS iterator to take into account the initial conditions
upon invocation.
Changed DFSPathIterator to DFSIslandIterator.

The new name is better-suited to the actual behavior of the Iterator class.
Preliminary tests for DFSIslandIterator.
Added an equality method for Graphs.

Not yet implemented in concrete classes though.
Changed the internal representation of adjacency list to a hash map.

Simplifies the code now that it is represented as a hash map. :)
Removed unnecessary lines.
Better exception message in make_neighbor.