Typo fixes, expand a few comments

[melissalinkert]

Mostly as the PR title indicates, but note:

• Line 227 adds -noflat, which shouldn't matter for CMU-1-Small-Region.svs (which has no pyramid), but matters a lot for most real-world SVS input data (which will have a pyramid).
• Line 2013 adds -series 0 to be consistent with the earlier cropping example.
• If running this locally, Windows won't be supported (things like wget aren't available). Worth asking on the upstream PR if that's needed though, since it's not a quick fix.
• Since it doesn't run on Windows and I don't have a suitable non-Windows environment, probably just needs a quick double-check that everything runs without error before opening the upstream PR.