DRY Ideas controller

Set the Idea based on the slug with a 'before_action' before the show,
edit, and update actions.
Remove example routes from config/routes.rb
Authenticate users before certain Idea actions

Authenticate the user making requests before performing any Idea
actions that would modify the database in any way.
Finish searching against Ideas

  - Create an action 'search' in the Ideas controller to collect all
    ideas that match the search text and render the 'ideas/search'
    view.
  - Create a basic 'ideas/search' view for showing the search results.
  - Route to the ideas#search action with a 'GET' request
  - Use 'pg_search' gem to create a search scope to look for ideas that
    match the search text through their titles, descriptions, or
    statuses in addition to the names/titles of any users, tags, or
    currents the idea is associated with.