Standard markdown > Make space after `>` in blockquotes optional
Standard markdown > Fix broken HTML inside list paragraphs
Assign GFM markdown a different main scope

This removes ambiguity
MultiMarkdown > Import GFM instead of standard Markdown

MultiMarkdown syntax file doesn't redefine things, instead imports standard markdown syntax file. With this commit, it imports GFM syntax file instead of the standard one. GFM has had many bug fixes and improvements over the standard md syntax file. So hopefully, multimarkdown users will benefit from this improvements, too.