Do not rely on dropdowns to create the menu

Renders the top menu correctly even if there are no dropdown menus, that
is, if the user wants to use a flat top menu.
Fix void variable error
Make the qrcode plugin optional
Insert the disqus plugin only when needed
Updated twitter bootstrap module path
Merge pull request #87 from jschweinsberg/master

Updated twitter bootstrap module path
Merge pull request #86 from d-p/feature/optional-plugin-qrcode

Make the qrcode plugin optional
Merge pull request #85 from d-p/feature/optional-plugin-disqus

Insert the disqus plugin only when needed
Merge pull request #83 from lunaryorn/patch-1

Fix void variable error
Merge pull request #82 from lunaryorn/fix-top-menu

Do not rely on dropdowns to create the menu