Added a more thorough description of Kruskal's algorithm.
Some revision in the description of Kruskal's algorithm.
Rewrote description of Prim's Algorithm.
Updated solutions to MST and ImageSegMST labs.
Some typo fixes for the MST lab.
Renamed MST lab file to reflect that it covers more than Kruskal's
algorithm.
Also renamed the solutions to the MST lab.
Merge pull request #254 from insertinterestingnamehere/mst

MST algorithm description rewrite.