add chai assertion lib

package.json

@@ -23,6 +23,7 @@
   },
   "license": "MIT",
   "devDependencies": {
+    "chai": "^3.5.0",
     "mocha": "^2.5.3"
   }
 }

test/test.js

+var assert = require('chai').assert;
+
 it('doesn\'t do anything', function(){
 
 });