HolyOrders should use pysolrtornado

[crantila]

Currently, HolyOrders crafts its own requests to Solr with Tornado. But I'm already maintaining a library for that—why not just use it instead?

[crantila]

One difficulty is that, in HolyOrders I want to avoid making things faster with asynchronous requests to either Drupal or Solr. I think I can use the Tornado IOLoop's run_sync() function to help with this.

[crantila]

Maybe pysolr-tornado should grow the capability to do synchronous requests?

The "making things go too fast for Solr" isn't as big of a deal as the need to guarantee that we don't call commit() before all the add() calls finish.