Guardfile: for now let haml and sass process doc

… instead of running make
add "medium-small" size: 420px
include 1em spacing between 2 column layout
add aspectRatios to Interactives embedded in doc

This makes it much easier to determine correct height
when embedding in the first column in the doc by displaying
these in the Interactive Browser.
adjust template for Pendulum to work at width: 420px

Question:

I'd like the right template element used for the graph
to take all the space (minus padding) from model.right
to interactive.right.

But trying either one of these plausible solutions fail:

  "width": "interactive.width-model-width",

Or:

  "right": "interactive.right",
correct relative reference to logo image
doc: embed interactives 420px wide, correct aspect ratios