Adding `raw` to output of @help_content

Given that `@help_content` is raw HTML from the controller: https://github.com/documentcloud/documentcloud/blob/276bd3e3d8ffbeb689508066dad55697c0e43776/app/controllers/workspace_controller.rb

I think you have to use `raw` to override Rails 4.0 default sanitizing 
 
Example problem pages:

- http://www.documentcloud.org/help/api
- http://www.documentcloud.org/featured
Merge pull request #90 from dannguyen/patch-1

Adding `raw` to output of @help_content