This fix reduces the duplicate call to backers when unique_backers() is called.
Current pledged amount is fetched in a single database query, without any PHP loop required.
Filter campaign payments to only include confirmed or preapproved payments. Added filters for extendability. Fixed typo in time_remaining().
Merge pull request #392 from Studio164a/studio164a/campaign-performance

Studio164a/campaign performance
Fixes a shipping bug that caused addresses outside the US or Canada to have the incorrect value. Also, updating repo to latest version for anyone who has been burned by the broken version on the .org plugin.