Differentiate admins and all CAS users

This allows anyone to log into the USG site, but normal users won't see
anything different.

There is currently no way to make a user an admin through the web
interface, but something like
  User.all.map{|u| u.update_attribute(:is_admin, true) }
should ensure the same functionality.

This adds a controller before_filter :authenticate_admin! which will
ensure the user is an admin, as well as a helper current_user_is_admin?
to mimic user_signed_in?, but for admins.
Stick the footer to the bottom of the browser

Use the technique here:
  http://ryanfait.com/resources/footer-stick-to-bottom-of-page/
to attach the footer to the bottom of the browser.

Basically, this puts all non-footer body content in a div with a
negative margin-bottom equal to the height of the footer.

This alone is enough to position the footer always at the bottom of the
page; but when the body content is too long it overlaps the footer, this
step is not enough. For this, a "push" div is added to make sure there
is at least #footer's height of blank space at the bottom of <body> for
the footer to overlap.
Implement static part of homepage

The homepage has some static content on the top, namely the logo, nav
links, and the special high-priority links ("Feedback Form", "Submit
Disbursement", "Search")

This implements a design for the top of this page.
Fixing merge
HAMLize header partial

Haml is cool. ERB kinda sucks.
HAMLize application layout.
Sort out header vs. navigation partials

To me "header" doesn't indicate shared navigation links, it means the
stuff inside <head>...</head> that's shared amongst layouts. It also
makes sense to have navigation links as a partial (since they, too, are
consistent among layouts).

This commit moves all <head> goodies into
layouts_partials/header.html.haml and the navigation links to
layouts_partials/navigations.html.haml.

Note: this skips the admin layout -- it will be refactored in the next
commit.
HAMLize admin template

It's really similar to application.html.haml -- maybe there is a
potential to combine the two layouts.
Remove unnecessary local variables.

This isn't actually being used for anything. I was testing to see if I
could get this working, but I couldn't quickly enough. So, I removed the
other traces of this, except is this file! Oops.
Extract logo + navigation to a partial

I hate seeing duplicate code -- this abstracts the logo + navigation
into a partial.
Make USG logo link to homepage

Clicking on the USG logo should take users back to the homepage. It now
does.
Remove noisy.js, install tiled bg image

Noisy.js is cool and a neat idea. However, it has a number of drawbacks:
* It makes inspecting HTML tiresome, since you must first scroll past
  the background image.
* When <body> doesn't cover the whole window the noise stops early,
  causing a visual bug.
* It is not cached; thus it adds render time to _every_ pageview.
* When I started using it I had not heard of http://subtlepatterns.com/

This removes noisy.js and replaces it with a tiled background image.
It's faster (probably), cachable, and fixes a visual glitch!
Trying to merge tom
Remove is_admin? after merge from tom
Tidying up and halfway through making navigation editable