The issuer operated by @dsschult generates the various standard time-related claims as floats. We think this is valid according to RFC; however, if the resulting token is passed to scitokens-cpp for verification, a std::bad_cast exception is thrown.

Two requests:

1. Instead of an exception message like: Failed to deserialize SciToken: std::bad_cast, catch the error and generate a human-friendly error message.
2. Relax the requirement and accept floats for iat, nbf, and exp.