[better-testing] initiate our markup/style testing by "photographing" rendered pages via phantomjs

We need some test coverage of our look.

The plan is to use only-web.rb and phantomjs to render certain pages into .pngs for quick comparison.

In order to be useful this needs to be specific. So lets say we'll start with doing "photos" of servers list screen and overview screen. We'll expand coverage as part of further stories.

So deliverable is a command that'll render html page with images of screenshots of "pages" mentioned above. In further stories we might add some additional tools to ease comparing of this "sets of images" between versions.