refactor: Remove require extension filename

lib/realtime.js

@@ -12,13 +12,13 @@ var chance = new Chance()
 var moment = require('moment')
 
 // core
-var config = require('./config.js')
-var logger = require('./logger.js')
-var history = require('./history.js')
+var config = require('./config')
+var logger = require('./logger')
+var history = require('./history')
 var models = require('./models')
 
 // ot
-var ot = require('./ot/index.js')
+var ot = require('./ot')
 
 // public
 var realtime = {