Refactored code, added param to MFA required to get passing credentials, added options hash to add_accounts for webhooks.

I have refactored much of the code making it more lightweight than before. All tests are now passing after adding a param to the MFA method, and adding an extra param to the add_account param allowing for users to add webhooks. 

Tests for webhooks are still needed. More tests can be written to cover various types of MFA, and inital adding of accounts with special options. Updates to the readme are still needed showing examples of the returned statements.