improved backer specs and prevented projects not online from being recommended [fix #55610112]
now we show only rewards that are not sold out yet in the reward selection [fix #56311666]
now we just let the thank_you_backer_id until it's overwritten by another one to avoid problems with redirection after some payment methods [fix #45832539]
Merge pull request #318 from diogob/bug_fixes

Bug fixes