Implement window.location redirection script

See `src/shim.html`. The strategy is as follows:

  1.  GET: `host.com/search/q=star`
  1.  nginx tries to serve the file `WWW_ROOT/search/q=star`
  1.  No such file, so nginx responds (should be 301/302) with `shim.html`
  1.  `shim.html` runs its `<script>`, matches `/search/`, and re-writes `window.location` to `/#/search/q=star`
  1.  nginx sees GET: `/`
  1.  nginx returns `index.html`, and the browser still has `location.hash="/#/search/q=star"`
  1. `require.js` load the application, `backbone.router` takes over using `location.hash`

@romanchyla @aholachek :
See in-line comments, especially the point about regex vs string matching and dealing with multiple '#'s. Feedback expected!