Revert chai removal.

- chai still needed for browser use.

Author: davidlehn

package.json

@@ -31,6 +31,7 @@
     "xmldom": "0.1.19"
   },
   "devDependencies": {
+    "chai": "^3.5.0",
     "commander": "^2.8.0",
     "cors": "^2.7.1",
     "express": "^4.13.3",

tests/test.js

@@ -64,7 +64,7 @@ if(_nodejs) {
   require('../' + _jsdir + '/jsonld');
   jsonld = jsonldjs;
   window.Promise = require('es6-promise').Promise;
-  var assert = require('assert');
+  var assert = require('chai').assert;
   require('mocha/mocha');
   require('mocha-phantomjs/lib/mocha-phantomjs/core_extensions');
   var program = {};