cli: Don't pass our proxy settings to the player.

Resolves #260.
chunchyroll: initial implementation of the API object
crunchyroll: removed expiration from the API (to avoid complexity) and finished the plugin
crunchyroll: added options
crunchyroll: added extra check when parsing the given url
crunchyroll: modified behavior to allow un-authenticated access. Premiun-only streams report a NoStreamsError
crunchyroll: rework api creation to use username & password when credentials don't work
crunchyroll: use cache to store auth and session credentials
crunchyroll: remove crunchyroll-credentials cli option
crunchyroll: remove debug prints
crunchyroll: added dateutil to the dependencies of the package
crunchyroll: added documentation
crunchyroll: always reinstantiate the session
crunchyroll: added purge_credentials option to clean the cache from credentials

This is useful when you need to recreate the session for the server to "forget"
the data stored in your previous session.
e.g. when trying to access over a proxy, your old session will contain
information about your region, forbidding you to access to region locked
content even if your proxy is within that region.