Document and refactor

Add TomDoc code documentation for these objects:
 * MyGists module
 * MyGists::Fetch
 * MyGists::Tags
 * MyGists::Fetch::Options
 * MyGists::Secure
 * MyGists::Refresh
 * MyGists::ActsAsTaggableOnExtensions
 * MyGists::GithubSession
 * Rename MyGists::GitHubSession
 * Users::OmniauthCallbacksController
 * ApplicationController
 * HomeController
 * TagsController
 * ActsAsTaggableOn::TagDecorator
 * GistDecorator
 * ProfileDecorator
 * ApplicationHelper
 * HelpHelper
 * HomeHelper
 * ProfileHelper
 * TagsHelper
 * Gist
 * Profile
 * GitHub
 * User
 * MyGists.Fetch CoffeeScript

Fefactor a bit:
 * Remove Gist.find_page_by_tag_name_and_profile since we can use Profile.gists to get the records
 * Refactor ProfileDecorator#gists to ProfileDecorator#gists_for so we do not overload the models gists association