Throw an error if configure() is called with unrecognised options.

lib/common.js

@@ -29,6 +29,13 @@ var common = {
       return _default;
   },
 
+  validateOptions: function(options, validKeys) {
+    for (var key in options) {
+      if (validKeys.indexOf(key) < 0)
+        throw new Error('Unrecognized option: ' + key);
+    }
+  },
+
   validParams: function(params) {
     var keys = Object.keys(params), i = keys.length;
     while (i--) {

lib/permessage_deflate.js

@@ -1,10 +1,22 @@
 'use strict';
 
 var ClientSession = require('./client_session'),
-    ServerSession = require('./server_session');
+    ServerSession = require('./server_session'),
+    common        = require('./common');
+
+var VALID_OPTIONS = [
+  'level',
+  'memLevel',
+  'strategy',
+  'noContextTakeover',
+  'maxWindowBits',
+  'requestNoContextTakeover',
+  'requestMaxWindowBits'
+];
 
 var PermessageDeflate = {
   configure: function(options) {
+    common.validateOptions(options, VALID_OPTIONS);
     var opts = this._options || {};
     for (var key in opts) options[key] = opts[key];
     return Object.create(this, {_options: {value: options}});