Add directed, undirected graphs
Add graph.AppendAdjacencyList()
Add queues, breadth-first search

- Add queues.Queue.
- Add breadth-first search for graphs.
queue.go: More idiomatic .Pop()
binary_searchable.go: Add Depth()
Add Height(), .InsertAll()

- binary_searchable.go: Add Height() function to get height of a tree
- binary_search_tree.go: Add .InsertAll() method to add variable number
  of elements.
binary_searchable.go: Add IsBalanced()
directed_graph.go: Add .RouteExists()
Add binary trees; search and red-black extend them
Add BFS, DFS for trees
binary_traversable.go: Add IsBinarySearchTree()