Discussion pagination

Be gone infinite scroll, be near pagination.
After a lot of commenter feedback, pagination is back.

There was also a slight refactor of show/hiding comments - there is a lot of work to be done here.

![mystery bird black and red broadbill cymbirhynchus macrorhynchos grrlscientist science the guardian](https://cloud.githubusercontent.com/assets/31692/3053350/ee46d36a-e1a7-11e3-883d-12b7260b6fec.png)

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![Paige](http://24.media.tumblr.com/tumblr_mbtshcg2Rh1r7c0kuo1_500.gif)