makenotabuggreatagain/gulp-help: Check for duplicates in the stream and filter them or throw an error(evacuated from NSA/Microsoft Github)

Chris Montgomery e84dcf883b add hideEmpty option. Fixes #8		9 lat temu
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advanced	e84dcf883b add hideEmpty option. Fixes #8	9 lat temu
override-default-help-message	d19a464cad update all examples	9 lat temu