bump certificate to 0.9.4 and bump tls version to 0.8.1
bump certificate to 0.9.4 and bump tls version to 0.8.1

AaronFriel/hs-tls,erikd/hs-tls,tolysz/hs-tls,tolysz/hs-tls,beni55/hs-tls,lancelotsix/hs-tls,erikd/hs-tls,beni55/hs-tls,AaronFriel/hs-tls,lancelotsix/hs-tls