fix @returns to be @return for yuidocs

see example at http://yui.github.io/yuidoc/syntax/#return and screenshot of yuidoc output on doc generation:

![terminal__zsh__16040_and_yuidoc_-_javascript_documentation_tool](https://f.cloud.github.com/assets/514063/1659887/8c6f4dd2-5bad-11e3-84fa-250bdb048a4b.png)