Adds pm ls

installed.go

@@ -1,4 +1,24 @@
 package pm
 
+import "sort"
+
 // Installed tracks installed packages.
 type Installed map[Name]Meta
+
+// Traverse returns a chan of Meta that will be sanely sorted.
+func (i Installed) Traverse() <-chan Meta {
+	r := make(chan Meta)
+	go func() {
+		names := Names{}
+		for n := range i {
+			names = append(names, n)
+		}
+		sort.Sort(names)
+
+		for _, n := range names {
+			r <- i[n]
+		}
+		close(r)
+	}()
+	return r
+}