- Add graph colouring example notebook

[unna97]

Note:

1. The gif generated gets converted to a png of just the first image

2. The notebook generates interactive folium maps that are currently added via screenshots

3. The maps can be uncommented to embed HTML

Solves: Notebook on Coloring Algorithms #77

[unna97]

@rossbar Here's the notebook with the removed HTML. Please note the code produces an animation as well that is converted to a png for the first image of the animation. Command used: jupyter nbconvert graph_colouring.ipynb --to markdown --output graph-colouring/graph_colouring.md