Fix outdated require()

This fixes an outdated require() call still pointing to 'node-subunit'
rather than 'subunit-js'.

index.js

@@ -14,7 +14,7 @@
 'use strict';
 
 var fs = require('fs');
-var subunit = require('node-subunit');
+var subunit = require('subunit-js');
 
 function SubunitReporter(helper, logger, config) {
   config = config || {};