Bug/sort facets

Fix for #235 (closed)

Putting up this MR as a WIP. I was about to write tests but when I started looking at the response from the fixture, I wasn't getting an ordered hashmap. But when I run it locally, I do. So, I was going to dig deeper into figuring out the methods for the test fixtures that get the response.

A couple of observations: I changed the code to this: 70a4b8a8 to get the ordered hashmap instead of copying and pasting the code from the master branch because I wasn't sure what data structure I was getting from the solr response (I didn't hook up the master branch to an existing solr to see this). This is a little convoluted and there is a clojure library that can do this as a one liner, but I would need to add it to the project dependencies and I wasn't sure if that was ok.

If this is totally wrong, apologies. I'd be curious to see what approach you take. Thanks.