Update dependencies

[bboyle]

A number of dependencies are out of date or no longer supported.

pxToEm: http://www.filamentgroup.com/lab/retaining_scalable_interfaces_with_pixel_to_em_conversion_archived/

history: http://tkyk.github.io/jquery-history-plugin/

[bboyle]

Consider this history plugin: https://github.com/browserstate/history.js