Fix username

Author: Swaggeroo

models/User.js

@@ -13,7 +13,7 @@ let generateAuthToken = function(sub, admin, otp, needOtp) {
 
 let validate = function (jsonObj) {
     const schema = Joi.object({
-        username: Joi.string().min(4).max(50).required().alphanum(),
+        username: Joi.string().min(4).max(50).required(),
         email: Joi.string().min(5).max(255).required().email(),
         password: passwordComplexity().required()
     });