fix #4063 -- share server is sending the wrong MIME type for css files
fix #4063 -- share server is sending the wrong MIME type for css files

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