Add require statements for Rails 3

We've been seeing some issues with Rails 3 applications unable to find
the `StaticPage` module.

* Add custom require for Rails 3
* Update quotes to match new style guide

https://github.com/thoughtbot/high_voltage/issues/146
Fix travis and appraisals

* Update appraisal usage and travis configuration to follow appraisals
  documentation.
* Use build matrix to exclude certain Ruby / Rails version combinations
* Don't ignore gemfiles/*