Add left/right X & up/down Y ranges

[demark]

Hi, it would be great if we'll can specify for example:
<img src="..." data-lxrange="200" data-rxrange="50" data-uyrange="50" data-dyrange="0">

[cameronmcefee]

What would be the usecase for something like this?

Doing something like this would create some weird visual effects. Currently plax is set up so that the start location of each object is assumed to be at the 50% point of it's range. This means that there is an even movement velocity as the mouse travels from 0% to 100% across the browser. If you were to specify uneven ranges via the suggested method, the object would inherit one velocity for the left side of the range, and get a different velocity for the right side.