Fix some PhpStorm inspection warnings

I added [PHPDoc](http://www.phpdoc.org/) tags (like [@property](http://www.phpdoc.org/docs/latest/references/phpdoc/tags/property.html)) to correct some [PhpStorm](https://www.jetbrains.com/phpstorm/) inspection warnings.

#### Example

[This line](https://github.com/samybob1/Ratchet/blob/master/src/Ratchet/ConnectionInterface.php#L17) corrects a warning when I use the `Session` property.

Before :
![before](https://cloud.githubusercontent.com/assets/2417752/4693915/a5144016-57b2-11e4-9709-6ba5d57df977.png)

After :
![after](https://cloud.githubusercontent.com/assets/2417752/4693916/ad66f466-57b2-11e4-8373-c4da4b62ebfc.png)