Slider: Controlled Range with allowCross=false has issues

[lap123]

Here is a demo: https://codepen.io/anon/pen/LzwzEW

Specifically, with 3 ranges or more, when cursor i is moved, cursors from i+2 and beyond are set to the value of i+1. Cursors from i-2 and before are set to i-1 value.

[paranoidjk]

@benjycui

Seems ensureValueNotConflict logic is wrong when there is over 3 handle.

Right now it haven't consider about the beeing processed value index in the whole bounds array, which cause all satisfy index > curHandle && value > curValue condition's handle got set to current handle value.

And it may need to handle pushable situation at the same time.

[Robin-front]

@paranoidjk agree.
I think I had fixed at #304 , I add index to ensureValueNotConflict, please check.