Add python 3 to travis
Add python 3 to travis

This is a bit ugly but I don't think you can do better with matrix.include
cherryc/dynet,Abasyoni/dynet,Abasyoni/dynet,Peilun-Li/dynet,cherryc/dynet,Peilun-Li/dynet,Abasyoni/dynet,Peilun-Li/dynet,cherryc/dynet