Reformat about.html, embed vimeo demo video.

Add:
        templates/about.html. static/(sass/about.sass, js/about.js)
                -Embed our Vimeo video, and add the Javascript necessary to make
                it fluid-width.

Ref:
        templates/about.html
                -The file's indented formatting was completely mangled in a
                previous commit; reformat.
Replace scalable-video JS solution with pure CSS.

Add:
        static/(sass/about.sass, js/about.js)
                -Convert `adjustVimeoDimensions()`, which created the
                fluid-dimensioned Vimeo video, to a pure CSS solution.