Redirect old WebUI downloads page to new one

There are currently a number of sites on the Internet that link to the old
downloads_web_ui.html page, including some popular blog posts. Since the WebUI
has been moved onto the Consul page itself, these links are now broken.

This commit adds a 301 (to preserve SEO) redirect from the old page to the new
one.
Merge pull request #436 from hashicorp/sethvargo/redirect_web_ui_downloads

Redirect old WebUI downloads page to new one
Do not index "Jespen" code block

The word "Jespen" is one of our top keywords because it appears so many times
in the Jespen Testing page. This commit adds a comment to disable Google
indexing in that code block so we can better target keywords.