convert Scaffold_Command->render() to Utils\mustache_render()
help --gen: add test for combined man pages
introduce man.mustache
re-generate man pages
Add a search-replace option to skip guids.
Specify any columns to be skipped.
Merge pull request #464 from cyberhobo/sr-no-guids

Add a search-replace option to skip guids.
search-replace: the --dry-run flag should be last
search-replace: add test for --skip-columns

see #464
Merge pull request #462 from wp-cli/mustache-man

Use Mustache templates for man markdown