Plugin jsonp

Plugin to highlight JSONP responses, with in-built functionality to extract file data from Github and Bitbucket requests. Inspired from #240.

While this _could_ be achieved by modifying File Highlighter (e.g. #208), not all hosts are going to have CORS enabled, and one may genuinely want to highlight JSONP responses (perhaps some server status, per the examples page).

Live demo of this branch at http://nauzilus-prism.azurewebsites.net/plugins/jsonp-highlight/
Could you return `null` here? This is the only way to differentiate between "not supported" and just an empty file.
The same goes for the bitbucket handler.