GitHub.createToken support passing an OTP, thus supporting 2fa

[madhephaestus]

#292 was not resolved despite being marked resolved. With 2fa enabled, the API requires users to go out of pipeline (into a web browser) to generate tokens. This is problematic from an instructions standpoint.

This is also not necessary.

If create token took an OTP, then the users program could hold and prompt the user to the OTP that comes from SMS. The OTP can be added to the token request via this field:

https://developer.github.com/v3/auth/#working-with-two-factor-authentication

If the API had a field to accept the OTP, then the user would be able to use this library as standard or 2fa mode without user going out of pipeline to generate tokens.

[madhephaestus]

I built a snapshot, and implemented it and tested the API generation of tokens when the user has 2fa enabled! (I am very excited about this )

If you merge my PR and publish a new release i can close out all my issues that are stacked up blocked by this.