fix(config): use polling by default

This should have been set to `true` in 18514d6. It's reversed.

Author: vojtajina

lib/config.js

@@ -186,7 +186,7 @@ var Config = function() {
   this.colors = true;
   this.autoWatch = false;
   this.autoWatchBatchDelay = 250;
-  this.usePolling = false;
+  this.usePolling = true;
   this.reporters = ['progress'];
   this.singleRun = false;
   this.browsers = [];