Faster implementation of filter.

This implementation improves performance a lot:
- Not enabling filtering detached elements flag (like jQuery does) is as faster as jQuery
- Enabling the flag is only 3 times slower instead of 50, It performs better in loops, specially decreasing time when creating ghost parents.

 Fixes issue #177 
I have used Julien's test example for measuring times.
https://github.com/manolo/testissue146/commits/master
Based on this post: http://lgrammel.blogspot.com.es/2010/09/gwt-arraylist-hashset-and-jsarray.html we should use a JsArray, but that post is a bit outdated. HashSet seems to perform better in contains, but add performs worst. ArrayList has had a lot of improvements lately and the current implementation is almost a js array, I guess it should perform better than hashset but not 100% sure. Maybe we can do some kind of benchmarking or simply use JsArray or JsCache.