[BUG] highlighted bar animation on Y Axis for all bar charts is wrong and not same speed

[liuxuan30]

Easy to reproduce:

1. simply navigate to stacked bar chart in ChartsDemo
2. highlight the top bar or bottom bar, or the middle one
3. click options and choose animate Y, and watch the animation
   You will see the highlighted bar's rect animation is not correct, and the timing is not the same too. The highlighted bar should be same speed as the background bar's speed

Update:
This bug happens on stacked horizontal bar chart, normal bar chart, all bar charts type, as long as we have highlighted the bar.

[liuxuan30]

For the speed issue, I change y2 = (ranges?.last?.to ?? 0.0) * Double(_animator.PhaseY) to y2 = (ranges?.last?.to ?? 0.0) * Double(1) will solve it, though I am not quite clear why.

It seems because prepareBarHighlight will multiply _animator.phaseY again, so it causing the animation slower?

    /// Prepares a bar for being highlighted.
    internal func prepareBarHighlight(#x: CGFloat, y1: Double, y2: Double, barspacehalf: CGFloat, trans: ChartTransformer, inout rect: CGRect)
    {
        let barWidth: CGFloat = 0.5

        var left = x - barWidth + barspacehalf
        var right = x + barWidth - barspacehalf
        var top = CGFloat(y1)
        var bottom = CGFloat(y2)

        rect.origin.x = left
        rect.origin.y = top
        rect.size.width = right - left
        rect.size.height = bottom - top

        trans.rectValueToPixel(&rect, phaseY: _animator.phaseY) <---
    }

[danielgindi]

Well I see the problem, but your suggestion does not solve it.
Interesting bug... Looking into this