With less emphasis on teaching CodeRefinery lessons, I have removed
the CR lesson summaries and teaching philosophies.
I have combined "the future of teaching" talk with the preparation
page - no need to have two pages, I guess.
De-emphasize "the science of teaching", put it at the bottom. While
it is probably useful, I put the longest things at the bottom so
that people will get through the shorter things first. Plus, it may
be too academic for some of our audience.
Review: check if the removed things are OK to remove.