[token-server] Implement rate limiting by IP

Summary: Getting scripted faucet hits again. Implement rate limiting by IP address.

Test Plan:
npm test. Unfortunately I am not sure how to test this without just testing the dependency. Dependency is well maintained.

Note though the teamcity failure when rate limiting was implemented on all routes -- unit tests failed as, well, we have more than 10 unit tests and they are executed immediately.

Still, expect to have iterations to tweak this implementation depending on what we see.

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D16697