feat(draggable): keep container position prop if different than static

Author: vieron

src/jquery.draggable.js

@@ -76,8 +76,9 @@
     var fn = Draggable.prototype;
 
     fn.init = function() {
+        var pos = this.$container.css('position');
         this.calculate_dimensions();
-        this.$container.css('position', 'relative');
+        this.$container.css('position', pos === 'static' ? 'relative' : pos);
         this.disabled = false;
         this.events();