Refactor encryption.Cipher to be an Encrypt/Decrypt Interface

All Encrypt/Decrypt Cipher implementations will now take
and return []byte to set up usage in future binary compatible
encoding schemes to fix issues with bloat encrypting to strings
(which requires base64ing adding 33% size)

pkg/validation/options.go

@@ -38,7 +38,7 @@ func Validate(o *options.Options) error {
 
 	msgs := make([]string, 0)
 
-	var cipher *encryption.Cipher
+	var cipher encryption.Cipher
 	if o.Cookie.Secret == "" {
 		msgs = append(msgs, "missing setting: cookie-secret")
 	} else {