See https://github.com/idan/oauthlib/pull/265 for rationale.
In brief: raising any exception blows the stack, which is
inappropriate for a non-error state.

* Moved requires for cryptotoken changes so that you don't have to install
  the dependencies if you aren't going to use cryptotokens

* Add a method to generate crypto tokens for use as Bearer tokens
* Add a method to verify an incoming crypto token and unpack the header and
  claims
* Uses the PyJWT library

This is not JWT token support, merely a way to generate Bearer tokens that
won't have to be stored in a database but can self-validate and store
additional information that you see fit.