Added xunit to project.json
Added xunit to project.json

merbla/serilog,clarkis117/serilog,adamchester/serilog,skomis-mm/serilog,nblumhardt/serilog,colin-young/serilog,serilog/serilog,harishjan/serilog,ravensorb/serilog,serilog/serilog,nblumhardt/serilog,richardlawley/serilog,CaioProiete/serilog,adamchester/serilog,joelweiss/serilog,clarkis117/serilog,skomis-mm/serilog,harishjan/serilog,colin-young/serilog,merbla/serilog,joelweiss/serilog,ravensorb/serilog