Fix outdated faq on python3 compatibility question.
Fix outdated faq on python3 compatibility question.

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