Fix DocBlock statements for better compatibility with Doctrine Annotation libraries

[See this SO question](http://stackoverflow.com/questions/26536331/doctrine-annotation-exception-when-using-parse-query-in-symfony2).

Fixes #50 

[See DocBlock documentation for proper `@return` parameter](http://phpdoc.org/docs/latest/guides/docblocks.html), specifically the mention of [Annotations](http://phpdoc.org/docs/latest/guides/docblocks.html#annotations)