Add SNI, NOISE and CERTHASH protocol in py-multiaddr

[lla-dane]

Tracks: multiformats/multiaddr#181

Added SNI, NOISE, CERTHASH protocol in py-multiaddr in reference with go-multiaddr

SNI had the same codec configs as DNS in go-multiaddr

protoSNI = Protocol{
	Name:       "sni",
	Size:       LengthPrefixedVarSize,
	Code:       P_SNI,
	VCode:      CodeToVarint(P_SNI),
	Transcoder: TranscoderDns,
}

So just added this line in the protocol registry

Protocol(P_SNI, "sni", "domain"),

Did the same thing with NOISE

Added the CERTHASH protocol as per go implementation

var TranscoderCertHash = NewTranscoderFromFunctions(certHashStB, certHashBtS, validateCertHash)

func certHashStB(s string) ([]byte, error) {
	_, data, err := multibase.Decode(s)
	if err != nil {
		return nil, err
	}
	if _, err := mh.Decode(data); err != nil {
		return nil, err
	}
	return data, nil
}

func certHashBtS(b []byte) (string, error) {
	return multibase.Encode(multibase.Base64url, b)
}

func validateCertHash(b []byte) error {
	_, err := mh.Decode(b)
	return err
}

[lla-dane]

Also added a test case for sni multiaddr as given in go-multiaddr tests

[lla-dane]

@acul71: Can you please take a look why these checks are failing with my changes, I am not understanding.

[lla-dane]

Added the certhash protcol, along with the test-suite