Core: Remove ISU specific references and add to default css.

## Ready State: Yes

Removes site specific references to make more generic. Adds more
css to provide a more polished default. Removes common modules
from drupal-org.make. Updates README with small amount of install
instructions regarding missing common module dependencies in
drupal-org.make.

## Requirements & Dependencies

* None

## Deployment Instructions

* Merge code.
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Browse to A-Z sitemap and view better styling