<ion-range> keeps sliding after releasing mouse outside the browser window

[ghost]

Short description of the problem:

What behavior are you expecting?

That it stops sliding after releasing the mouse outside the browser windows.

Steps to reproduce:

1. Press the slider
2. Move your cursor outside the browser window
3. Release the mouse
4. Move your cursor to the slider
5. The slider keeps sliding until you press and release the mouse again

Which Ionic Version? 2 Beta 8