Fix test errors and add mocha to jshint configs.

Can't fix "Expected an assignment or function call and instead saw an expression."
because chai uses properties to call an assertion.
Problem was discussed in: chaijs/chai#41

.jshintrc

@@ -1,5 +1,6 @@
 {
   "curly": true,
   "eqeqeq": true,
-  "undef": true
+  "undef": true,
+  "mocha": true
 }

test/integration/init_game.spec.js

@@ -1,3 +1,5 @@
+/* global nsn: true, expect: true */
+
 describe('main', function(){
 
   describe('initGame()', function(){
@@ -12,6 +14,6 @@ describe('main', function(){
     it('resizes screen');
 
     it('runs Bootstrap init');
-  })
+  });
 
 });

test/unit/engine.spec.js

@@ -1,3 +1,5 @@
+/* global nsn: true, expect: true, sinon: true */
+
 describe('Engine', function(){
   before(function(){
     nsn.GameSound = sinon.stub();
@@ -30,6 +32,6 @@ describe('Engine', function(){
    it('has init()', function(){
      expect(nsn.Engine).to.respondTo('init');
    });
-  })
+  });
 
 });