Implementation of navbar and logout feature.

base.html: Adding site-wide navbar for navigation and accessing account
management/logout features.
base.css: styling to work with the added navbar.
urls.py: Adding a logout url.
views.py: Adding the logout view. Logs a user out and redirects to the
login page.
Navbar changes

Cleaning up site navbar for better user interaction.
Must still fix the mobile issue where the navbar is an extra 4px tall
when logged in due to the dropdown menu.
Navbar change #3

Better positioning of the account management drop down for mobile view.
Fix for firefox navbar collapse positioning

Setting the left navbar header to display:inline-block to ensure that
the collapse clears properly in the mobile version of firefox.