Added documentation and updated styles.

- added den-skeleton-app.txt which has descriptions of libraries used
- added helper-classes.txt which lists some of the more useful classes
- added basic css styles to style.css (majority of css is taken care of
with bootstrap)
- added base-styles to index pg to get a quick preview of how some
elements will look
- put navigation in a partial
- added den logo
- removed unnecessary files that come with zend skeleton app