[#30] Upgraded Bootstrap to v2.3.2, removed unused bootstraps

The updated version of bootstrap is not minified since minification is
handled by the asset pipeline (sprockets).

The less-rails-bootstrap gem was not doing anything so has been removed.

vendor/assets/stylesheets/bootstrap.css is unused and now removed.
Merge branch '30-upgrade-bootstrap'
[#33] Remove unused routes, controller actions and templates
Merge branch '33-remove-unused-actions-views-routes'
[#35] Article#search exceptions reported to Rollbar in staging, prod.

Instead of simply logging the error, pass the exception to our error
handling service (Rollbar).

This commit also introduces a best practice for error handling.
Merge branch '35-better-error-handling'
[#39] Writers can edit any article if it is a Draft
Merge branch '39-fix-writer-permissions'
[#37] Updated the gem
[#37] Upgrade admin dashboard to use new syntax

dashboards.rb -> dashboard.rb
[#37] Updated active_admin initializer to use built in cancan adapter

Removed explicit authorization check in controllers.
[#37] f.buttons deprecated for f.actions (formtastic)
[#37] Update the active_admin named route used in the footer
[#37] Dashboard page has highest priority (first element in nav)
[#37] Fixing the admin stylesheets

* Removed duplicated stylesheet active_admin_custom
* Tabs to spaces, remove trailing whitespace
* Wrap custom changes to admin styles in the admin scope (new feature of
  activeadim 0.6_
[#37] Fix the JS function which hides the 'articles' admin page
[#37] Remove unused JS function from active_admin.js

Looks like this maybe used to be responsible for moving between guide
steps on the main site, but it isn't doing anything currently.
[#37] Fix admin dashboard permissions (useless use of proc)
[#37] Constant for the article status
[#37] Fixed button styles when editing article as writer or editor

Necessitated changing the javascript a bit so we can use the normal
ActiveAdmin classes on the buttons without it triggering the usual form
submission.

Removed the confusing "Commit to editing" input for editors and replaced
it with a dropdown of users: editors can now freely assign writers to
articles.

Removed the also confusing and broken "Review by <email>" status field
for admin users, so that now you cannot assign an editor to an article.