start implementing a graph data structure
Make sure not self loops exist in the internal representation of a graph

Merge branch 'master' of github.com:topliceanu/learn

* 'master' of github.com:topliceanu/learn:
  improve comments
  finished alpha version of the graph library in python
  start implementing a graph data structure

Conflicts:
	algo1/src/graph.py
	algo1/src/minimum_cut.py