Adding an http route for /lita/help to list commands via a web page
Adding documentation for the web help feature
Web help fixes

* Added a template_root method
* Updated the web_help method to use the global template_root
* Fixed method call syntax in template
* Adding requires to lita.rb
Added more tests

* Simplified the ERB file
* Errors are handled (slightly) better
Updates to web-help addition

* Added a url_for method to build URLS
* Added a public_url config option for rooting URLs
* Added test to ensure proper url generation
Merge pull request #19 from webdestroya/web-help

Ability to reply to 'help' with a URL containing a list of commands