Move pipes up to Ch1

[trevorcampbell]

to align better with the Python book (which essentially had to do chaining in ch1 to avoid insanely verbose code)

would also simplify the first two weeks of worksheets a little bit

this is not urgent at all though -- I'm not dead-set on doing this either. Py was forced to do it, so it would be nice to be consistent, but if it's significantly worse to do it that way in R we can leave as-is.