Add dotenv to automatically load variables from .env

app.js

@@ -2,6 +2,8 @@
 
 'use strict';
 
+require('dotenv').config();
+
 var express = require('express');
 var path = require('path');
 var favicon = require('serve-favicon');

package.json

@@ -27,6 +27,7 @@
     "crypto-js": "3.1.9-1",
     "debug": "~2.6.0",
     "decimal.js": "7.2.3",
+    "dotenv": "^6.2.0",
     "electrum-client": "github:chaintools/node-electrum-client#43a999036f9c5",
     "express": "^4.16.4",
     "express-session": "1.15.6",