Add slider thumbnail reel feature

![screen shot 2014-10-17 at 10 49 36 am](https://cloud.githubusercontent.com/assets/2614324/4681671/38b82c50-5615-11e4-9035-0453602d5cdc.png)


I'd probably create the thumbreel and thumbnails at the same time and then append them to the DOM in one go to avoid the perf hit of multiple DOM updates and layout thrashing.