Intermediate: Switch to using the official bootstrap-sass

(instead of the deprecated bootstrap-sass-rails)
Remove unlinked "installing komodo edit" page now that the "Editors" page exists

The most current instructions for installing a given editor are probably best left to the editor's website.
Tighten up TOC in 'learn to code' by not showing gifs and svgs in it
TOC: Skip markdown image links like ![cool image](cool_image.jpg)
Group site links on 'docs' page into hopefully-logical sets
Titleize irb and ARGV
a few edits to the teacher training deck
Learn To Code tweaks