[revert] [refactor] Remove usuless indexof dependency (#582)

This reverts commit 6043c49.

lib/socket.js

@@ -5,6 +5,7 @@
 var transports = require('./transports/index');
 var Emitter = require('component-emitter');
 var debug = require('debug')('engine.io-client:socket');
+var index = require('indexof');
 var parser = require('engine.io-parser');
 var parseuri = require('parseuri');
 var parseqs = require('parseqs');
@@ -736,7 +737,7 @@ Socket.prototype.onClose = function (reason, desc) {
 Socket.prototype.filterUpgrades = function (upgrades) {
   var filteredUpgrades = [];
   for (var i = 0, j = upgrades.length; i < j; i++) {
-    if (~this.transports.indexOf(upgrades[i])) filteredUpgrades.push(upgrades[i]);
+    if (~index(this.transports, upgrades[i])) filteredUpgrades.push(upgrades[i]);
   }
   return filteredUpgrades;
 };

package.json

@@ -29,6 +29,7 @@
     "debug": "~2.6.9",
     "engine.io-parser": "~2.1.1",
     "has-cors": "1.1.0",
+    "indexof": "0.0.1",
     "parseqs": "0.0.5",
     "parseuri": "0.0.5",
     "ws": "~2.3.1",