Fix the return annotation for fetch_access_token
Return annotation description needs changing as well as type
Revert "RAQ : Allow referral code to be supplied with all API calls."

This reverts commit 02a6c20839372d31c050c633be9f100442ba59e8.
cancel bills via the API
Merge pull request #28 from gocardless/pr/27

Fixed pull request for @RQuadling's comments
Merge pull request #24 from sampart/annotation-change

Fix the return annotation for fetch_access_token
Merge pull request #29 from gocardless/cancel-bill

cancel bills via the API
Allow the referrer (via the 'r' parameter) to be passed without signature failure.