Made exceptions runtime

Let's not bother with catching exceptions, since we know they're not
supposed to happen. (For now)
Added edge traversal.

A robot can move from a node to another through an edge using the
traverse method.
Added get parent method for node.

In the graph/tree representation, the parent node is the one that
connects to edge 0. Exception to that is node 0, which is the root of
the tree.
Added node related methods to World class

-Clone which node the robot is on
-getting which node the robot is on
-Adding node (incomplete)
Created hypothesis class

-expanding hypothesis (incomplete)
-validating hypotheses
-collapsing implied hypothesis
-getting unconnected hypothesis