Drag Plugin
===========

The `drag` plugin allows for modifying the planet's projection's rotation with the mouse wheel. It supports dragging vertically with hard stops at the north and south poles, and dragging horizontally without restriction.

API
---

**`planetaryjs.plugins.drag([config])`**

Valid keys for `config` are:

* `onDrag`, `onDragStart`, `onDragEnd`: hooks to the `d3.behavior.drag` object's `drag`, `dragstart`, and `dragend` events; each defaults to a no-op

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```javascript
planetaryjs.plugins.drag({
  onDrag: function() {
    console.log("The planet was dragged!", d3.event);
  }
});
```
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