Add search to spec

Added using Google custom search.  Removed the indexing block in https://github.com/Financial-Times/ft-origami/commit/c3e38612cfc79296a3c8f1dc345d32bb09f6d3eb, so need to wait until Google finishes indexing the site and then this can be merged.

When they're done, this will return results:

https://www.google.co.uk/webhp#q=site%3Aorigami.ft.com+%22Origami+is+about+empowering+developers%22