ADD support for 2fa

Github users may decide to enable 2-fa authentication to have more
security. Gost was not able to tell if a user had it enabled, and even
worse, it pretended everything worked by creating an empty configuration
file.

Users can now create a token whether they have 2-fa enabled or not.

REF #11

Details:
* ADD support for 2-fa
* ADD informations when posting anonymously
* REFACTOR authentication to check response was successfull
Merge pull request #14 from MaximeD/support-two-factor-authentication

ADD support for 2fa