Reference security audit in README (#2468)
Reference security audit in README (#2468)

Signed-off-by: Chris Aniszczyk <2a3e0ec6821d10bf53e535c46e422f24d94584b5@gmail.com>
johnbelamaric/coredns,yongtang/coredns,johnbelamaric/coredns,chrisohaver/coredns,miekg/coredns,ii/coredns,ii/coredns,coredns/coredns,miekg/coredns