Full parse through UI

This is a huge commit. I parsed through the whole app and changed a bunch of stuff. Mostly best practices, but a several UI improvements as well.

This commit ...

* adds Table of Contents to all `.scss` files for easier scanning and editing.

* removes all non-semantic classes from the HTML and instead uses Sass mixins.
     	* rows
	* columns
	* panels
	* buttons
	*  alert-boxes

* creates Sass %placeholders for common elements

* adjusts settings.scss and app.scss
Merge branch 'master' of github.com:ushahidi/pingapp into ui-refactor

Conflicts:
	application/views/pages/groups/edit.php
	application/views/pages/messages/index.php
	application/views/pages/people/view.php
Merge pull request #105 from ushahidi/ui-refactor

Full parse through UI
Merge branch 'master' of github.com:ushahidi/pingapp into email-dev
Remove trailing slash from site_url