Override Blacklight's facet_limit partial to pass in facet name as sr-only

Closes #345 

#### Language Facet
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![language-facet](https://cloud.githubusercontent.com/assets/96776/3503899/4ccf680e-063b-11e4-8201-cdb677fd2747.png)


#### More Link Markup
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![more-languages](https://cloud.githubusercontent.com/assets/96776/3503901/5cfd0bc8-063b-11e4-968d-fef09ef005f8.png)