Feature/new datamodel

In typical recursive fashion, I set out to update the home page for bootstrap and ended up optimizing our javascript loads. This pull request boils down to:

* Load jquery from CDN in `<head>`, fall back to locally hosted version
* Load base template `<script>` tags right before closing `</body>`
* Rename *head_scripts* template block to *extra_scripts* for clarity

I can't load an exhibit at the moment on this branch so I haven't tested if these changes have any implications there. If optimizing right now seems crazy, we can shelf these commits until later. Just let me know and I'll stash patches somewhere.

Back to the homepage...or maybe that *discover* page.