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/stats/memory_notsupported.go

@@ -0,0 +1,7 @@
+// +build !linux
+
+package stats
+
+func (mem *MemStatus) fillInStatus() {
+	return
+}