Search for annotations any *.wikidot.com page returns all annotations for all *.wikidot.com pages

[wikidot](http://www.wikidot.com) serves wikis at `http://[wiki-name].wikidot.com` URLs. A search for annotations on any of these URLs returns all annotations for 'http://*.wikidot.com' pages.

Example query:
1. `curl 'https://hypothes.is/api/search?uri=http%3A%2F%2Fsandbox.wikidot.com%2F'`
2. Output: https://gist.github.com/robertknight/d882aef2cc9dce4fb284

Note that those annotations are all from different `http://[wiki-name].wikidot.com` pages.

This is happening because every wikidot page has a `` link in the ``.

Reported in https://hypothesis.zendesk.com/inbox/tickets/118

Start by running the example curl request against the API search endpoint and compare annotations from different *.wikidot.com pages. Trace how the wikidot rel="alternate" application/wiki link affects URI matching, then verify that searching one wiki URL no longer returns annotations from other wiki pages.

Written by the indexing model from the issue text.