Changed Gemfile source
Added more includes to spec helper
Moved out Renderer into a separate file. Renamed capturer to persistence.
Generating a slide now sets the last_generated time. Renderer is now an object that does not need instantiating, and is mocked in tests (speed improvement)
Added failing test for only re-generating expired slides, and added support to Slide for knowing whether it has expired
VisService now has ability to only regenerate expired slides