Implement TLS server

$ ./minio --tls --cert <your_cert> --key <your_private_key>

This patchset also provides crypto/x509 - which is a wrapper package
to generate X509 certificates.

This is necessary to provide certificates later through management console

pkg/httpserver/tlshelpers.go

@@ -0,0 +1,29 @@
+package httpserver
+
+import "crypto/tls"
+
+func getDefaultTLSConfig() *tls.Config {
+	config := &tls.Config{}
+
+	//Use only modern ciphers
+	config.CipherSuites = []uint16{
+		tls.TLS_RSA_WITH_AES_128_CBC_SHA,
+		tls.TLS_RSA_WITH_AES_256_CBC_SHA,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
+		tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
+		tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
+		tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+	}
+
+	//Use only TLS v1.2
+	config.MinVersion = tls.VersionTLS12
+
+	// Ignore client auth for now
+	config.ClientAuth = tls.NoClientCert
+
+	//Don't allow session resumption
+	config.SessionTicketsDisabled = true
+	return config
+}