Update deps without licenses

The following packes did not have discernible LICENSE files at the hash we have
vendored:
  github.com/beorn7/perks
  github.com/daviddengcn/go-colortext
  github.com/garyburd/redigo
  github.com/prometheus/common
  github.com/shurcooL/sanitized_anchor_name
  github.com/stretchr/objx

This commit updates all of them and updates the central LICENSE file.

vendor/github.com/prometheus/common/model/labelset.go

@@ -27,6 +27,21 @@ import (
 // match.
 type LabelSet map[LabelName]LabelValue
 
+// Validate checks whether all names and values in the label set
+// are valid.
+func (ls LabelSet) Validate() error {
+	for ln, lv := range ls {
+		if !ln.IsValid() {
+			return fmt.Errorf("invalid name %q", ln)
+		}
+		if !lv.IsValid() {
+			return fmt.Errorf("invalid value %q", lv)
+		}
+	}
+	return nil
+}
+
+// Equal returns true iff both label sets have exactly the same key/value pairs.
 func (ls LabelSet) Equal(o LabelSet) bool {
 	if len(ls) != len(o) {
 		return false
@@ -90,6 +105,7 @@ func (ls LabelSet) Before(o LabelSet) bool {
 	return false
 }
 
+// Clone returns a copy of the label set.
 func (ls LabelSet) Clone() LabelSet {
 	lsn := make(LabelSet, len(ls))
 	for ln, lv := range ls {