update billing for devkit2
fixed device flag for fake billing, use isSimulator
Use faux billing for debug builds
fix crash on ios if no bundleID
fix getPurchases error preventing handling old purchases

getPurchases has an error (which is in a giant generic try catch) which
prevents handling non-consumed transactions on the store. This is a
major issue -- if there are every non-consumed transactions, the user's
device will query the store (and fail) every ten seconds, forever, AND
the purchases will never be consumed.
add purchaseWithReceipt event
add transaction signatures to android
add purchaseWithReceipt event
update readme for devkit2 and new event

- update to devkit2 imports
- add info about setting up google play store purchases
- add section about `purchaseWithReceipt` event
Merge pull request #8 from gameclosure/feature-receipts

Feature receipts