Change to go1.6.1 and vendoring

vendor/github.com/yudai/umutex/umutex.go

@@ -0,0 +1,38 @@
+// Package umutex provides unblocking mutex
+package umutex
+
+// UnblockingMutex represents an unblocking mutex.
+type UnblockingMutex struct {
+	// Raw channel
+	C chan bool
+}
+
+// New returnes a new unblocking mutex instance.
+func New() *UnblockingMutex {
+	return &UnblockingMutex{
+		C: make(chan bool, 1),
+	}
+}
+
+// TryLock tries to lock the mutex.
+// When the mutex is free at the time, the function locks the mutex and return
+// true. Otherwise false will be returned. In the both cases, this function
+// doens't block and return the result immediately.
+func (m UnblockingMutex) TryLock() (result bool) {
+	select {
+	case m.C <- true:
+		return true
+	default:
+		return false
+	}
+}
+
+// Unlock unclocks the mutex.
+func (m UnblockingMutex) Unlock() {
+	<-m.C
+}
+
+// ForceLock surely locks the mutex, however, this function blocks when the mutex is locked at the time.
+func (m UnblockingMutex) ForceLock() {
+	m.C <- false
+}