doc: fix grammar, spelling, punctuation
I restrained myself to making only changes that turn bad English into
good English. There are still opportunities to improve, but other
changes require some discussion and review. This change should be
uncontroversial.
syntax: re
/figures/[^/]+\.png$
^docs/build/
^docs/html/
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$