Add possibility to specify starting position

Author: cjblomqvist

lib/draggable.js

@@ -143,6 +143,25 @@ module.exports = React.createClass({
 		 */
 		grid: React.PropTypes.arrayOf(React.PropTypes.number),
 
+		/**
+		 * `start` specifies the x and y that the dragged item should start at
+		 *
+		 * Example:
+		 *
+		 * ```jsx
+		 * 	var App = React.createClass({
+		 * 	    render: function () {
+		 * 	        return (
+		 * 	            <Draggable start={{x: 25, y: 25}}>
+		 * 	                <div>I start with left: 25px; top: 25px;</div>
+		 * 	            </Draggable>
+		 * 	        );
+		 * 	    }
+		 * 	});
+		 * ```
+		 */
+		start: React.PropTypes.object,
+
 		/**
 		 * `zIndex` specifies the zIndex to use while dragging.
 		 *
@@ -235,6 +254,10 @@ module.exports = React.createClass({
 			handle: null,
 			cancel: null,
 			grid: null,
+			start: {
+				x: 0,
+				y: 0
+			},
 			zIndex: NaN,
 			onStart: emptyFunction,
 			onDrag: emptyFunction,
@@ -254,7 +277,7 @@ module.exports = React.createClass({
 			offsetX: 0, offsetY: 0,
 
 			// Current top/left of this.getDOMNode()
-			clientX: 0, clientY: 0
+			clientX: this.props.start.x, clientY: this.props.start.y
 		};
 	},