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_supported.go

@@ -0,0 +1,18 @@
+// +build linux
+
+package stats
+
+import (
+	"syscall"
+)
+
+func (mem *MemStatus) fillInStatus() {
+	//system memory usage
+	sysInfo := new(syscall.Sysinfo_t)
+	err := syscall.Sysinfo(sysInfo)
+	if err == nil {
+		mem.All = uint64(sysInfo.Totalram) //* uint64(syscall.Getpagesize())
+		mem.Free = uint64(sysInfo.Freeram) //* uint64(syscall.Getpagesize())
+		mem.Used = mem.All - mem.Free
+	}
+}