Add empty TabListType

Add option to set empty tablist for people who wants to disable TabList.


Empty TabList on 1.8:

![2014-09-08_00 30 49](https://cloud.githubusercontent.com/assets/4775112/4179966/ef233328-36de-11e4-9b94-253621a1a2e1.png)


Empty TabList on 1.7:

![2014-09-08_00 32 17](https://cloud.githubusercontent.com/assets/4775112/4179967/fa23f24e-36de-11e4-9d63-5ee1e0dac87c.png)

It's empty but you're setting it to the global one? Did you mean new Empty( this )?