Adding xunit-perf-api command line options to readme (#1300)
Adding xunit-perf-api command line options to readme (#1300)

* Adding xunit-perf-api command line options to readme

* adding period at end of sentence.

* Change project.json to csproj

adamsitnik/corefxlab,dotnet/corefxlab,Vedin/corefxlab,tarekgh/corefxlab,VSadov/corefxlab,adamsitnik/corefxlab,VSadov/corefxlab,ahsonkhan/corefxlab,benaadams/corefxlab,VSadov/corefxlab,stephentoub/corefxlab,benaadams/corefxlab,Vedin/corefxlab,VSadov/corefxlab,VSadov/corefxlab,joshfree/corefxlab,hanblee/corefxlab,Vedin/corefxlab,ericstj/corefxlab,stephentoub/corefxlab,ericstj/corefxlab,stephentoub/corefxlab,stephentoub/corefxlab,dotnet/corefxlab,joshfree/corefxlab,KrzysztofCwalina/corefxlab,ericstj/corefxlab,VSadov/corefxlab,whoisj/corefxlab,ericstj/corefxlab,stephentoub/corefxlab,ericstj/corefxlab,KrzysztofCwalina/corefxlab,hanblee/corefxlab,Vedin/corefxlab,ahsonkhan/corefxlab,tarekgh/corefxlab,ericstj/corefxlab,Vedin/corefxlab,stephentoub/corefxlab,whoisj/corefxlab,Vedin/corefxlab