Merge pull request #308 from dreamsxin/gridfs

Add class Phalcon\Mvc\Collection\GridFS
Add Phalcon\Image::NARROW
Merge pull request #309 from dreamsxin/gridfs

Add method Phalcon\Mvc\Collection\GridFS::write
Merge pull request #310 from dreamsxin/image_update

Add Phalcon\Image::NARROW
Add class Phalcon\Mvc\Model\Metadata\Mongo and Phalcon\Mvc\Model\Metadata\Cache
Change method name Phalcon\Mvc\Collection\GridFS::save to saveFile