Update cmux to 0.1.4

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

vendor/github.com/soheilhy/cmux/cmux.go

@@ -116,8 +116,9 @@ type cMux struct {
 func matchersToMatchWriters(matchers []Matcher) []MatchWriter {
 	mws := make([]MatchWriter, 0, len(matchers))
 	for _, m := range matchers {
+		cm := m
 		mws = append(mws, func(w io.Writer, r io.Reader) bool {
-			return m(r)
+			return cm(r)
 		})
 	}
 	return mws