Conceptually, a Page object is a lot more than just the HTML it contains; it's also a DOM and a JS state. Hence the counterintuitiveness of #to_s returning only the document's innerHTML.
Envjs is now a normal gem dep
Latest changes have been released, no more need for specific envjs commit.
Not automatically pulled in by Johnson prerelease. Reportedly a Rubygems bug
Johnson lib doesn't run on 1.9 http://github.com/jbarnette/johnson/issues#issue/21