webapp: handle .Rmd files like Markdown
webapp: handle .Rmd files like Markdown

tscholl2/smc,sagemathinc/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,DrXyzzy/smc,tscholl2/smc,DrXyzzy/smc,tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,sagemathinc/smc,tscholl2/smc