[Objects: Node] Implemented possibility to add colors to nodes.
[Drawer] Added support to the graphdrawer to draw the colors given in the node.
[Algorithms: GreedyCol] Implemented a greedy color algorithm and added a test to check for the behavior and correct code execution.
[IPython Notebook] Added IPython notebook to prove the greedy coloring algorithm.
[Tests] Adjusted the greedy coloring algorithm test.
[Tests] Adjusted name of the greedy col test.
[Tests] Adjusted test to catch several allowed states.
[Tests] Test added for the minimum_check in the greedy col algorithm to increase test coverage.