Adds customizable range min and max values to Size control

Allows clients to customize the smallest and largest possible pen sizes
that users can select using the range slider.

```javascript
var board = new DrawingBoard.Board(board.id, {
  size: 5,
  controls: [
    "Color",
    "DrawingMode",
    {
      Size: {
        range: {
          min: 5,
          max: 50
        }
      }
    },
  "Navigation"
  ]
});
```