Add application/xml as whitelisted text mimetype (fixes issue168).
Add application/xml as whitelisted text mimetype (fixes issue168).

rietveld-codereview/rietveld,supriyantomaftuh/rietveld,robfig/rietveld,fuzan/rietveld,openlabs/cr.openlabs.co.in,fuzan/rietveld,google-code-export/rietveld,berkus/rietveld,foolonhill/rietveld,Koulio/rietveld,sajingeo/rietveld,arg0/rietveld,xtypebee/rietveld,openlabs/cr.openlabs.co.in,arg0/rietveld,DeanHere/rietveld,gavioto/rietveld,nbodepallictr/touchites-test,draem0507/rietveld,ericmckean/rietveld,ericmckean/rietveld,supriyantomaftuh/rietveld,aungzanbaw/rietveld,xtypebee/rietveld,nbodepallictr/touchites-test,nbodepallictr/touchites-test,rietveld-codereview/rietveld,andyzsf/rietveld,xtypebee/rietveld,supriyantomaftuh/rietveld,google-code-export/rietveld,gco/rietveld,Koulio/rietveld,gco/rietveld,ericmckean/rietveld,andyzsf/rietveld,v3ss0n/rietveld,kscharding/integral-solutions-smxq,robfig/rietveld,v3ss0n/rietveld,google-code-export/rietveld,nareshboddepalli/touchites-codereview,sajingeo/rietveld,kscharding/integral-solutions-smxq,nbodepallictr/touchites-codereview,nbodepallictr/touchites-codereview,nareshboddepalli/touchites-test,nareshboddepalli/touchites-test,nbodepallictr/touchites-codereview,nareshboddepalli/touchites-codereview,fuzan/rietveld,salomon1184/rietveld,dushmis/rietveld,DeanHere/rietveld,rietveld-codereview/rietveld,nareshboddepalli/touchites-codereview,kscharding/integral-solutions-smxq,gavioto/rietveld,berkus/rietveld,gavioto/rietveld,robfig/rietveld,aungzanbaw/rietveld,sajingeo/rietveld,salomon1184/rietveld,aungzanbaw/rietveld,rietveld-codereview/rietveld,openlabs/cr.openlabs.co.in,dushmis/rietveld,foolonhill/rietveld,Koulio/rietveld,salomon1184/rietveld,draem0507/rietveld,v3ss0n/rietveld,DeanHere/rietveld,nareshboddepalli/touchites-test,gco/rietveld,foolonhill/rietveld,arg0/rietveld,draem0507/rietveld,dushmis/rietveld,andyzsf/rietveld,berkus/rietveld