2 Factor Authentication Support

[surdaft]

I wanted to use this but with 2 Factor Authentication enabled I was returned with:

discord-cli - version: v0.3.0-DEVELOP

*Starting Session...2016/10/27 09:54:46 Session Failed
2016/10/27 09:54:46 Unable to fetch discord authentication token. <nil>

[Sense545]

Managed to get this working. Requires new method in discordgo as well.
Will fork, commit and submit some pull requests later when I have time.

[RickvanLoo]

Thank you, and please do. @Sense545 Stuff like this makes me consider picking it up again. I don't use the client anymore, but if people see any future in it then sure 😄

[Sense545]

Ah, apparently this can get you banned... I guess we shouldn't do that.
Reference: discord/discord-api-docs#69 (comment)