Go port of DOM distiller

[markusmobius]

This might be useful to those who want to run DOM Distiller as a standalone program.

We ported the Java code to Go (without GWT and any Chromium dependencies):

https://github.com/markusmobius/go-domdistiller

It now works fine as a server-side program or command line program.

The stable branch is the most faithful port of Distiller (everything minus some parts where Distiller relies on some render-level info).

The master branch includes insights from Mozilla's readability.