Selectable Nodes Delegate

[jz709u]

-PointSelectedProtocol triggers on touch of node or bar
-changes to touchEnded when user lifts off at any points or bars then
return the label, value, and the point at which selected
-this is used for display for purposes or for presenting a popup at the
point location.

[smitaAcellere]

I did it. Thank you so much. You save my time.

[manuel21]

Hello this code has an issue that crash the app

// left point only
let leftPoint = graphPoints[leftDataPointIndex].location **//EXC_BAD_INSTRUCTION
![screen shot 2017-04-28 at 1 24 33 pm](https://cloud.githubusercontent.com/assets/7534410/25541951/363f686a-2c16-11e7-9123-c0daa320d608.png)
![screen shot 2017-04-28 at 1 24 33 pm](https://cloud.githubusercontent.com/assets/7534410/25541963/4244faee-2c16-11e7-853f-1512fb99725b.png)

**

        if shouldDrawBarLayer {
            let barWidthToRightOfX = locationOfTouchPoint.x + (barWidth / 2)
            if locationOfTouchPoint.y < leftPoint.y &&
                barWidthToRightOfX > locationOfTouchPoint.x {
                triggerDelegateWith(index: leftDataPointIndex)
            }

fatal error: Index out of range

The index is wrong when I Tap on the background instead of a point

[mithunmathew1990]

Please review #82
@manuel21 @philackm @jz709u

[mithunmathew1990]

In func triggerDelegateWith(index: Int) {
guard 0 <= index && index <= (labels.count - 1) else { return }

Isn't it supposed to be
guard 0 <= index || index > (labels.count - 1) else { return }