Linguistic features and autocomplete

This adds support for 31 languages, exact search (e.g. for source code), phonetic search (so you can match e.g. "Zach Galifianakis" to "zack galafanackes"), and autocomplete.

It depends on a previously submitted patch to update sunspot's solr version to 4.1, so you probably want to commit that before reviewing this in depth.

The interesting part of the test suite is here: https://github.com/fizx/sunspot/commit/30004487ec60d0d42205a1d55bc1be55234bc2ee#L1R116