Added pm.Meta

meta.go

@@ -0,0 +1,23 @@
+package pm
+
+import "errors"
+
+type Meta struct {
+	Name        string `json:"name"`
+	Version     string `json:"version"`
+	Description string `json:"description"`
+	Namespace   string `json:"namespace"`
+}
+
+func (m *Meta) Valid() (bool, error) {
+	if m.Name == "" {
+		return false, errors.New("name cannot be empty")
+	}
+	if m.Version == "" {
+		return false, errors.New("version cannot be empty")
+	}
+	if m.Description == "" {
+		return false, errors.New("description cannot be empty")
+	}
+	return true, nil
+}