Add basic bundle, spec, and config types

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

config.go

@@ -0,0 +1,18 @@
+package containerd
+
+type Process struct {
+	Args []string
+	Env  []string
+	Cwd  string
+	Uid  int
+	Gid  int
+	TTY  bool
+}
+
+type Config struct {
+	Process    Process
+	Hostname   string
+	Domain     string
+	Labels     map[string]string
+	StopSignal int
+}