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/.travis.yml

@@ -0,0 +1,13 @@
+language: go
+
+before_install:
+  - go get github.com/stretchr/testify
+
+go:
+  - 1.7
+  - 1.8
+  - 1.9
+  - tip
+
+script:
+  - go test -v ./...