issue(toggle): tapping the label should activate the toggle action.

[ionitron-bot]

Ionic version: (check one with "x")
[ ] 1.x
[x] 2.x

I'm submitting a ... (check one with "x")
[x] bug report
[ ] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/

Current behavior:
On the Toggle control (http://ionicframework.com/docs/v2/components/#toggle) when you tap the ion-label in the ion-item, the ion-toggle does not activate the toggle and switch states.

This should work exactly as per the Checkbox control (http://ionicframework.com/docs/v2/components/#checkbox) when clicking/tapping on the ion-label. Or anywhere in the ion-item.

Expected behavior:
The toggle should be activated and switch states when it's ion-label is clicked/tapped.

<ion-item>
  <ion-label> Sam</ion-label>
  <ion-toggle disabled checked="false"></ion-toggle>
</ion-item>

This occurs on version 2.2.0.