Rename variable used for poll interval.
Add rate limiting to message forwarding.
Change to subscribe test to use 'fire immediately' terminology.
Add tests for rate limiting.
Allow for longer timeouts across all tests.
Increase delays on SQS tests to give AWS a chance to update.
Allow variable poll interval in case of long processing.
Merge branch 'feature/1-rate-limit' into develop
Update README.
Bump version number.
Merge branch 'release/0.3.0' into develop