Cleanup: remove unused index.html

I first noticed an unused footer element, but it turned out that
the whole `index.html` file was unused (it is now generated by
`index.underscore`)
Replace .execute() for .click() behavior in Nightwatch tests
Cleanup: Remove unused nv.d3

stats are removed now and we don't use it any more

Closes COUCHDB-2355
New design for docs

Port from #33:

Based on the work of Jenn Schiffer <jenn@pancaketheorem.com>
(@jennschiffer), Sue Lockwood <deathbear@apache.org>
(@deathbearbrown) and Sean Barclay (@seanbarclay)
Fix the flash on doc page route changes

This is subtle and only occurs on Chrome. To reproduce:
1. Go to the Database -> All Docs page for a database.
2. Click from the All Documents page to All Design Docs.

Click back and forth a few times. Notice that sometimes there's a
sort of quick flash that appears over the breadcrumbs section making
it look a little like the breadcrumbs are being re-rendered.

Closes COUCHDB-2467