Fix unhandled promise rejection on ms auth

[IceTank]

The authenticate function that does ms auth returns a promise that can reject on error. If this occurs in your code the node process will exit due to an unhandledRejection error. This pull requests fixes this and instead emits a error event on the client.

[rom1504]

can you please resolve conflicts ?

[nickisnoobatcode]

Looks good to me, would be great if this could be merged.