Add missing type to Role properties definition

Fix "created" and "modified" to be defined with type "date".

common/models/role.json

@@ -12,11 +12,12 @@
       "required": true
     },
     "description": "string",
-
     "created": {
+      "type":"date",
       "defaultFn": "now"
     },
     "modified": {
+      "type":"date",
       "defaultFn": "now"
     }
   },

test/role.test.js

@@ -96,6 +96,14 @@ describe('role model', function() {
     });
   });
 
+  it('should generate created/modified properties', () => {
+    return Role.create({name: 'ADMIN'})
+      .then(role => {
+        expect(role.toJSON().created).to.be.instanceOf(Date);
+        expect(role.toJSON().modified).to.be.instanceOf(Date);
+      });
+  });
+
   it('should define role/user relations', function(done) {
     User.create({name: 'Raymond', email: 'x@y.com', password: 'foobar'}, function(err, user) {
       if (err) return done(err);