directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/command/signal_handling.go

@@ -0,0 +1,31 @@
+// +build !plan9
+
+package command
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func OnInterrupt(fn func()) {
+	// deal with control+c,etc
+	signalChan := make(chan os.Signal, 1)
+	// controlling terminal close, daemon not exit
+	signal.Ignore(syscall.SIGHUP)
+	signal.Notify(signalChan,
+		os.Interrupt,
+		os.Kill,
+		syscall.SIGALRM,
+		// syscall.SIGHUP,
+		syscall.SIGINT,
+		syscall.SIGTERM,
+		// syscall.SIGQUIT,
+	)
+	go func() {
+		for _ = range signalChan {
+			fn()
+			os.Exit(0)
+		}
+	}()
+}