use chai for improved string diffing

package.json

@@ -39,6 +39,7 @@
     "test-browser-local": "npm run pre-test-browser && zuul --local 8080 -- test/context-test.js test/scanner-test.js test/parse-test.js test/render-test-browser.js"
   },
   "devDependencies": {
+    "chai": "^2.3.0",
     "eslint": "^0.20.0",
     "mocha": "^2.1.0",
     "zuul": "^2.1.1"

test/helper.js

@@ -1,2 +1,4 @@
-assert = require('assert');
+var chai = require('chai');
+assert = chai.assert;
+chai.should();
 Mustache = require('../mustache');

test/render-test.js

@@ -20,7 +20,7 @@ describe('Mustache.render', function () {
         output = Mustache.render(test.template, view);
       }
 
-      assert.equal(output, test.expect);
+      output.should.equal(test.expect);
     });
 
   });