added python tutorial stub
added python tutorial stub

This should be helpful to people until someone gets around to writing python documentation in the official docs.
cherryc/dynet,Peilun-Li/dynet,Abasyoni/dynet,mitchellstern/dynet,cherryc/dynet,Peilun-Li/dynet,Abasyoni/dynet,Abasyoni/dynet,cherryc/dynet,kamigaito/cnn,Peilun-Li/dynet,mitchellstern/dynet,kamigaito/cnn