Added documentation and assertions for appid and classid.
Documentation and spacing cleanup to fit within margins.
I think we're good with that now.  Hopefully.
Added "transfer amount" parameter to a new addItem() method.
Added handling for amount of added currency.
You can see how much currency has been added by (TradeInternalCurrency) item.getTradedAmount().
Currency is removed when the amount is set to 0.
Reflected addition of handling amount of added currency.
String variables that point to null and are assumed to be non-null Strings are bad, mmmmkay?
Also changed some if / getType to optType in TradeEvent and rearranged the TradeSession update method to handle errors before anything else.
Merge branch 'master' of https://github.com/nosoop/SteamTrade-Java.git