Fix ion-reorder drag and scroll stuck to top or bottom of screen.

[pfiaux]

Short description of what this resolves:

When dragging an item on a scroll view it will scroll the view when the top/bottom of the screen is reached. However it keeps scrolling until it reaches the top or bottom of the content even if the dragged item isn't on the edge.

Changes proposed in this pull request:

• New drag events where dragged item no longer cause scrolling stop scrolling
• Add a cap on the maximum scroll speed

Ionic Version: 1.3.3

Fixes: #224