refactor(config.js): Extract config file

* Separate different config source to each files
* Freeze config object

lib/models/index.js

@@ -3,13 +3,14 @@
 var fs = require('fs')
 var path = require('path')
 var Sequelize = require('sequelize')
+const {cloneDeep} = require('lodash')
 
 // core
 var config = require('../config')
 var logger = require('../logger')
 
-var dbconfig = config.db
-dbconfig.logging = config.debug ? logger.info : false
+var dbconfig = cloneDeep(config.db)
+dbconfig.logger = config.debug ? logger.info : false
 
 var sequelize = null