fix error in Grid.getNodeAt(int x, int y) by vyo on 25/10/2013

method incorrectly returned the node at position (x , x*y)
now correctly returns the node at position (x , width*y)
fix error in Node.equals(Object node) method by vyo on 25/10/2013

The method used an unreliable means of comparing the neighbour
arrays of the compared nodes.
Now uses Array.equals() to guarantee the intended functionality.
modify functionality of Dijkstra.getPath method by vyo on 25/10/2013

getPath used to compute the shortest path from origin to destination,
followed by backtracking through the nearest neighbours along the
path. Finally the path elements' order had to be reversed.
Now the path from destination to origin is being computed to
eliminate the need for reversing the path.
modify author name on class by vyo on 25/10/2013

Was manu, has been changed to vyo to reflect github repo owner.