Ordered Query Strings

Sort query string parameters before comparing them, to allow for systems that parse URI query-strings in different orders.

If a request fails verification, raise an error that indicates specifically what failed and why.
WARNING Client systems should be careful not to expose these exception messages to untrusted systems.

v2.1.1: Merge pull request #18 from envato/fix-jwt-version-incompatibility

Lock JWT dependency to 1.5.x