Redirect proof of concept

[migurski]

I’ve added a means of doing redirects in the docs.

In the mkdocs config, it looks for a section like this:

redirects:
  'old-thing': 'get-started'
  'offsite-stuff': 'http://example.com'
  'search': 'besmirch'

The example configures three redirects: old-thing is redirected to get-started, offsite-stuff is redirected to http://example.com, and search is not redirected at all because it's a real page that exists.

• [x] Build the thing for Mapzen JS docs.
• [x] Talk to @rmglennon and @kkowalsky to determine whether it should be used.
• [x] Add it to the rest of the docs.

[rmglennon]

I'm going to try this with my mobility changes!

[migurski]

Great! I can help when we do the merging and pushing of Extracts tomorrow.