Standardize and materialize 500, 404, and 403 pages

**In this PR:**
- Removed bootstrap CSS
- Added inline Material Design Lite CSS
- Added a single CSS file for ease of editing, which can be minified and copy+pasted into the inline styles
- Updated CSS (changed old red to new red, removed extraneous CSS)
- Added very basic tab-selection function
- Added sad bucky
- Moved alternate links into tabs (uw-system links are shown by default and uw-madison links can be seen by clicking the uw-madison tab)
- Added `npm` to serve locally for dev purposes
- Updated readme

**Note:** Previously, bootstrap CSS was being brought in via CDN and other styles were added via `<style>` tags. Using the latter approach for MDL looks pretty gory in the HTML. Can I use a CDN for that like we were doing for bootstrap or would that be considered a dependency?

### Screenshots
![Screen_Shot_2016-07-26_at_11.37.07_AM](/uploads/5a97126fdb94edc94a6a6b29b9b2faf8/Screen_Shot_2016-07-26_at_11.37.07_AM.png)
![Screen_Shot_2016-07-26_at_11.37.23_AM](/uploads/abfa0d61f2d1808b913dbdd9cf9cae03/Screen_Shot_2016-07-26_at_11.37.23_AM.png)
![Screen_Shot_2016-07-26_at_11.37.36_AM](/uploads/161fe9f24dc4a2950f934279659375b7/Screen_Shot_2016-07-26_at_11.37.36_AM.png)

Notify: @timothy-vertein @levett @michael-adas @andrew-petro 

See merge request !9