Replace dev depencency frank_jwt with jsonwebtoken

[clintfred]

As a developer running the tests,
I want an up to date, maintained, JWT library with minimal dependencies.

https://github.com/GildedHonour/frank_jwt is not being very actively maintained and it has a direct dependency on openssl. The openssl dependency makes running on windows require us to statically link openssl to compile the tests.

https://github.com/Keats/jsonwebtoken does not depend on openssl (using ring, instead, which we already depend on).

Directly related to #162
Could be related to #160