update test/max_listeners.js to use path.join for cross-platform compatibility see: #314 (comment)

Author: nelsonic

test/max_listeners.js

@@ -1,5 +1,8 @@
 var spawn = require('child_process').spawn;
-var ps = spawn(process.execPath, [ __dirname + '/max_listeners/source.js' ]);
+var path = require('path');
+
+var ps = spawn(process.execPath, [path.join(__dirname, 'max_listeners', 'source.js')]);
+
 ps.stdout.pipe(process.stdout, { end : false });
 
 ps.stderr.on('data', function (buf) {