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/filer/embedded_filer/directory.go

@@ -0,0 +1,15 @@
+package embedded_filer
+
+import (
+	"github.com/chrislusf/seaweedfs/weed/filer"
+)
+
+type DirectoryManager interface {
+	FindDirectory(dirPath string) (filer.DirectoryId, error)
+	ListDirectories(dirPath string) (dirs []filer.DirectoryEntry, err error)
+	MakeDirectory(currentDirPath string, dirName string) (filer.DirectoryId, error)
+	MoveUnderDirectory(oldDirPath string, newParentDirPath string) error
+	DeleteDirectory(dirPath string) error
+	//functions used by FUSE
+	FindDirectoryById(filer.DirectoryId, error)
+}