Clean up index. Try to load local remark first.
Show where to find headers.
Add concepts and ufuncs sections.
Consistently use dark slide for topic announcement. Minor formatting fix.
Fix side-header formatting (too long).
Ufunc content update.
Merge branch 'stefanv/mid-flight'

Conflicts:
	slides/building_numpy.md
	slides/index.html.tmpl
	slides/intro.md
More pictures.