User can place a bid on a product.

@cgruppioni @SherrySeibel  - Please take a look.  The feature is limited to being able to place the bid.  No work has been done to display the bid in the views.  New user stories are in place for those items.
I didn't remove a line called number_to_currency(product.price).  If that's something you put in another branch, I'll just accept your version when I rebase.