added option for POST data to download()
added option for POST data to download()

sunlightlabs/congress-opencongress,unitedstates/congress,Nolawee/congress,chriscondon/billtext,chriscondon/billtext,boblannon/congress,Nolawee/congress,sunlightlabs/congress-opencongress,boblannon/congress,unitedstates/congress