A map like data structure based on Vec to represent a Graph with directed edges.

The goal is to be able to build a structure looking more like this: | \ | / \ \ | / / __\_\|/_/__ / /|\ \ / / | \ \ / | \ |

Instead of a tree like this: ____|____ __|__ __|__ | | | |

Further goals: [x] store and find node [x] store edges [] graph traversal along the edges [] generator function to exhaustively discover all paths from one node to another [] possible weights on edges