Passing name of the file to be created down into generators
Added 'rasterize' script for PhantomJS
Adding lodash/underscore as a dependency
In theory, this should help PDF generation by clearly delineating page boundaries

In practice, it doesn't seem to help.  But it doesn't seem to hurt anything w.r.t.
HTML generation so I left it in.
This adds a command-line option to create a script that can build a PDF of the presentation