button now determines upframe based on pointerOver

Fixes #156

The upFrame was previously just the same as the outFrame. I have changed it so on inputUp, it looks at pointerOver to decide if the mouse is still inside button, and chooses between outFrame and overFrame accordingly.

Because of this logic, there is now now need for a seperate upFrame, so I removed the properties.

This makes the buttons behave the same as browser/OS buttons, which feels more natural.