Adds location validations

So I lost interest in yo after about a week, but I was bored and saw that yo added some new features to their API. We already added in the ability to send your location via yoyo, but this PR adds some validations that yo ignores.

If you send an invalid location (not in their format of `latitude;longitude`) you get a 200 back but no yo is sent.

Their documentation also says not to send `location` and `link` together. Turns out they just ignore `location` and use `link`, but I say that is wrong and the yo should not be sent at all if that happens.

Also, they added the ability to create accounts via the API. Next time I am bored I will look at that.

Ciao!