Escape js with esc_js rather than json_encode for compatibility reasons

json_encode adds a backslash in one of the parameters where we don't want one.

See: https://github.com/GigaOM/gigaom/issues/6072

![screen shot 2014-12-10 at 4 26 18 pm](https://cloud.githubusercontent.com/assets/430385/5384648/4c3c7896-8089-11e4-9c49-19d36f700f1a.png)