Added group subcommand with add and delete commands

lib/util/slice.go

@@ -0,0 +1,12 @@
+package util
+
+// returns true if the needle exists in the haystack
+func ContainsString(haystack []string, needle string) bool {
+	for _, val := range haystack {
+		if val == needle {
+			return true
+		}
+	}
+
+	return false
+}