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/filer.go

@@ -0,0 +1,28 @@
+package filer
+
+type FileId string //file id in SeaweedFS
+
+type FileEntry struct {
+	Name string `json:"name,omitempty"` //file name without path
+	Id   FileId `json:"fid,omitempty"`
+}
+
+type DirectoryId int32
+
+type DirectoryEntry struct {
+	Name string //dir name without path
+	Id   DirectoryId
+}
+
+type Filer interface {
+	CreateFile(fullFileName string, fid string) (err error)
+	FindFile(fullFileName string) (fid string, err error)
+	DeleteFile(fullFileName string) (fid string, err error)
+
+	//Optional functions. embedded filer support these
+	FindDirectory(dirPath string) (dirId DirectoryId, err error)
+	ListDirectories(dirPath string) (dirs []DirectoryEntry, err error)
+	ListFiles(dirPath string, lastFileName string, limit int) (files []FileEntry, err error)
+	DeleteDirectory(dirPath string, recursive bool) (err error)
+	Move(fromPath string, toPath string) (err error)
+}