Use latest rubygems in appveyor
Use latest rubygems in appveyor

yui-knk/byebug,k0kubun/byebug,miamiruby/byebug,miamiruby/byebug,os97673/byebug,os97673/byebug,ozydingo/byebug,scalp42/byebug,guilherme/byebug,icebreaker/byebug,guilherme/byebug,webdev1001/byebug,icebreaker/byebug,yui-knk/byebug,yui-knk/byebug,scalp42/byebug,saisai/byebug,deivid-rodriguez/byebug,saisai/byebug,k0kubun/byebug,deivid-rodriguez/byebug,webdev1001/byebug,k0kubun/byebug,ozydingo/byebug,guilherme/byebug,deivid-rodriguez/byebug