remove code dup for constants

Author: lipp

src/websocket.lua

@@ -1,10 +1,12 @@
+local frame = require'websocket.frame'
+
 return {
   client = require'websocket.client',
   server = require'websocket.server',
-  CONTINUATION = 0,
-  TEXT = 1,
-  BINARY = 2,
-  CLOSE = 8,
-  PING = 9,
-  PONG = 10
+  CONTINUATION = frame.CONTINUATION,
+  TEXT = frame.TEXT,
+  BINARY = frame.BINARY,
+  CLOSE = frame.CLOSE,
+  PING = frame.PING,
+  PONG = frame.PONG
 }