feat: add upstream and verbose flags to command line interface

feat: add upstream support allowing to chain cache servers if needed
fix: tweaked garbage collection to be better

vfs/memory/memory.go

@@ -73,9 +73,8 @@ func (m *MemoryFS) Set(key string, src []byte) error {
 			int64(len(src)),
 			time.Now(),
 		),
-		data: make([]byte, len(src)),
+		data: src,
 	}
-	copy(m.files[key].data, src)
 
 	return nil
 }