make username unique and make username required

common/models/user.js

@@ -11,10 +11,14 @@ module.exports = function(User) {
   // set salt factor for passwords
   User.settings.saltWorkFactor = 5;
 
-  //User.validatesExclusionOf('username', {
-  //  inArray: blacklistedUsernames,
-  //  message: 'username is taken'
-  //});
+  // username should not be in blacklist
+  User.validatesExclusionOf('username', {
+    'in': blacklistedUsernames,
+    message: 'is taken'
+  });
+
+  // username should be unique
+  User.validatesUniquenessOf('username');
 
   debug('setting up user hooks');
   // send verification email to new camper