Support to USERNOTICE for subs, and variables for sub_plan

[Doc94]

Well this library sound great...
But i need support for new system of subs, plan subs prime,1000,2000,3000.

[Gikkman]

I had not noticed that they had extended the subscribers system that much.
Sure, I'll get around fixing that. I am currently on vacation, and won't be back till September, but I'll look at it then.

[Gikkman]

This was handled in #12