Pwned Passwords V2

Thanks to @PatF for contributing this!

Pwned Passwords V2 brings some new features

• a larger dataset
• a prefix based api removing the need to send full passwords to an external service
• frequency for each password hash returned
• the removal of rate limiting! (previously a big limitation for a server side library like this)

More details here: https://www.troyhunt.com/ive-just-launched-pwned-passwords-version-2/

This change is backwards compatible however there is one new optional config

# Minimum number of times a pwned password must exist in the data set in order
# to be reject.
config.min_password_matches = 10