2.0.0 - Starting to fix assets test-unit

Hello,

I have working a little on collection and filters assets classes.

I fixed 2 test-unit errors but know I have a "segmentation fault" on testFilterMultiplesSourcesFilterNoJoin function line 440.

Another things, zephir dynamic setter (example: protected _prefix { get, set }; on collection.zep line 30) doesn't return current object. Some tests of assetsTest.php use this feature.

Regards,