Tutorial: add checkpoints with live examples

[zaceno]

Also some minor tweaks

[codecov-io]

Codecov Report

Merging #890 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #890   +/-   ##
=======================================
  Coverage   20.32%   20.32%           
=======================================
  Files           1        1           
  Lines         187      187           
=======================================
  Hits           38       38           
  Misses        149      149

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