@1aurabrown => Place Bids

Adds the networking required to send the POST to submit a bid. Then sits at the confirmation page. Removes the `BiddingWebViewController.swift` 

Also:
* fixes #145 
* fixes #137 
* partial fix for #144
I'm also wondering if there's a more readable way to to this in RAC. It took me a lot of staring to figure out the logic flow here -- first checking to see if we already have a bidder for you in the nav context, then seeing if the server has any bidders for you and if so assigning it to the nav, if not creating a new bidder and assigning it to to the nav, etc. Maybe there are better RAC methods for this kind of thing than a chain of `.then{}`s that each contain a similar conditional? @AshFurrow  ?