add user model and password encryptation

src/libs/models/user.js

+var mongoose = require('mongoose');
+var Schema = mongoose.Schema;
+var bcrypt = require('bcrypt');
+
+var UserSchema = new Schema({
+  email:{
+    type: String,
+    required: true
+  },
+  password: {
+    type: String,
+    required: true
+  }
+});
+
+UserSchema.pre('save', function(next){
+  var user = this;
+  if(this.isModified('password') || this.isNew){
+    bcrypt.genSalt(10, function (err, salt){
+      if(err){
+        return next(err);
+      }
+      bcrypt.hash(user.password, salt, function(err, hash){
+        if(err){
+          return next(err);
+        }
+        user.password = hash;
+        next();
+      });
+    });
+  }
+  else{
+    return next();
+  }
+});
+
+UserSchema.methods.comparePassword = function(passw, cb){
+  bcrypt.compare(passw, this.password, function(err, isMatch){
+    if(err){
+      return cb(err);
+    }
+    cb(null, isMatch)
+  });
+};
+
+module.exports = mongoose.model('User', UserSchema);