add test for broken markdown regexp
force markdown regexp to match the full extension
jekyll build/serve -q option to docs
Expand the description for the `-q` option.
Merge pull request #3147 from blbradley/markdown-file-ext-regexp
Update history to reflect merge of #3147 [ci skip]
Merge pull request #3149 from jekyll/document-build-serve-quiet-option
Update history to reflect merge of #3149 [ci skip]