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Merge pull request #184 from davelab6/patch-1

Update README.md
also obfuscate name-IDs 16, 17 and 18
Merge pull request #185 from anthrotype/obfuscate3

[subset] also obfuscate nameIDs 16, 17 and 18, if present
One can't import fontTools.subset and fontTools.merge together

Fixes https://github.com/behdad/fonttools/issues/177