Incomplete list of valid arguments

[nferrari]

In some places, a verification is done to know if the user is providing valid arguments. I think the lists have some arguments names missing:

While creating a Check, I got a warning about the "tags" argument but it works. https://github.com/KennethWilke/PingdomLib/blob/master/pingdomlib/check.py#L66

While updating a Check, I got a warning about the "name" argument but it works. https://github.com/KennethWilke/PingdomLib/blob/master/pingdomlib/check.py#L356

I don't know if these missing arguments are the only one, that's why I can't yet provide a PR. If you think I can make one with only these 2, I will.

Regards,