model: added methods arg infos

I've noticed that the api reference in the docs doesn't match the @param-s specified in the source, and this can lead to this: http://forum.phalconphp.com/discussion/2050/how-to-use-model-skipattributes-i-failed-to-work-it-out-

The thing missing is the ZEND_BEGIN_ARG_INFO_EX macro for each method, that is used by the php ReflectionClass to get the method parameters.

I could do this work for all the classes but it's a big work to do, and i'd like to know what @phalcon has in mind to solve this (maybe there's a better way, maybe we have to wait for 2.0). Thanks.