Hi, just a very tiny edit in quickstart and readme

throughout quickstart you use the convention 

     import vincent
     vincent.Bar()
     vincent.Area()

etc. But then when you present Map you just type Map, without vincent, so I just edited documentation source and readme to make vincent.Map() so that it is consistent with the rest of docs.

It's a tiny pedantic change I know :) if it's helpful I'll be happy if not let's just forget about it :) Great project by the way!