Update setup.py with python3 and pyton2 exact classfiers.
Update setup.py with python3 and pyton2 exact classfiers.

crast/wtforms,skytreader/wtforms,jmagnusson/wtforms,wtforms/wtforms,Aaron1992/wtforms,hsum/wtforms,Xender/wtforms,subyraman/wtforms,cklein/wtforms,pawl/wtforms,Aaron1992/wtforms,pawl/wtforms