added reference to Utf8String
added reference to Utf8String

ericstj/corefxlab,stephentoub/corefxlab,KrzysztofCwalina/corefxlab,VSadov/corefxlab,hanblee/corefxlab,VSadov/corefxlab,Vedin/corefxlab,ericstj/corefxlab,VSadov/corefxlab,alexperovich/corefxlab,stephentoub/corefxlab,stephentoub/corefxlab,tarekgh/corefxlab,VSadov/corefxlab,whoisj/corefxlab,nguerrera/corefxlab,weshaggard/corefxlab,benaadams/corefxlab,benaadams/corefxlab,dotnet/corefxlab,ahsonkhan/corefxlab,KrzysztofCwalina/corefxlab,Vedin/corefxlab,tarekgh/corefxlab,whoisj/corefxlab,adamsitnik/corefxlab,ahsonkhan/corefxlab,Vedin/corefxlab,stephentoub/corefxlab,ericstj/corefxlab,Vedin/corefxlab,stephentoub/corefxlab,ericstj/corefxlab,VSadov/corefxlab,VSadov/corefxlab,ericstj/corefxlab,ravimeda/corefxlab,livarcocc/corefxlab,joshfree/corefxlab,stephentoub/corefxlab,Vedin/corefxlab,ericstj/corefxlab,adamsitnik/corefxlab,joshfree/corefxlab,hanblee/corefxlab,Vedin/corefxlab,dotnet/corefxlab