Create Graph::adjList and subobjects with null prototype (fix #76)
Merge pull request #75 from eush77/breadth-first-search

Add Breadth-First Search
Merge pull request #77 from eush77/adjlist-prototype-76

Create Graph::adjList and subobjects with null prototype (fix #76)
Return previous vertices in Bellman-Ford (as other shortest-path algorithms do)