First split into crockery init and crockery run

The init command creates a crockery.db file containing the domain name and
TLS keypair. The run command starts IMAP and SMTP services based on that file.

Supporting only a single domain is starting to look a bit unnecessary. We'll
see how that goes.

vendor/github.com/asdine/storm/codec/codec.go

@@ -0,0 +1,11 @@
+// Package codec contains sub-packages with different codecs that can be used
+// to encode and decode entities in Storm.
+package codec
+
+// MarshalUnmarshaler represents a codec used to marshal and unmarshal entities.
+type MarshalUnmarshaler interface {
+	Marshal(v interface{}) ([]byte, error)
+	Unmarshal(b []byte, v interface{}) error
+	// name of this codec
+	Name() string
+}