renamed jQuery adapter for Draggable class to $.fn.drag. Fixes #17.

Prevents name collisions with jQuery UI draggable module.

src/jquery.draggable.js

@@ -315,10 +315,10 @@
 
 
     //jQuery adapter
-    $.fn.draggable = function ( options ) {
+    $.fn.drag = function ( options ) {
         return this.each(function () {
-            if (!$.data(this, 'draggable')) {
-                $.data(this, 'draggable', new Draggable( this, options ));
+            if (!$.data(this, 'drag')) {
+                $.data(this, 'drag', new Draggable( this, options ));
             }
         });
     };

src/jquery.gridster.js

@@ -410,7 +410,7 @@
             }, 60)
           });
 
-        this.drag_api = this.$el.draggable(draggable_options).data('draggable');
+        this.drag_api = this.$el.drag(draggable_options).data('draggable');
         return this;
     };