old_contents: var express = require('express');
  var math = require('mathjs');
  var bodyParser = require('body-parser');
  
  var handlers = require('./lib/handlers');
  
  var app = express();
  
  app.set('port', (process.env.PORT || 8080));
  
  app.use(bodyParser.urlencoded({ extended: true }));
  
  app.listen(app.get('port'), function () {
    console.log('app starting at port '+ app.get('port'));
  });
  
  var mathParser = new math.parser();
  
  handlers.setMathParser(mathParser);
  
  app.get('/eval', handlers.evalGet);
  app.post('/eval', handlers.evalPost);
  
  app.get('/scope/read', handlers.scopeReadGet);
  
  
new_contents: var express = require('express');
  var request = require('request');
  var math = require('mathjs');
  var bodyParser = require('body-parser');
  
  var handlers = require('./lib/handlers');
  
  var app = express();
  
  app.set('port', (process.env.PORT || 8080));
  
  app.use(bodyParser.urlencoded({ extended: true }));
  
  app.listen(app.get('port'), function () {
    console.log('app starting at port '+ app.get('port'));
    
    var appName = process.env.APP_NAME;
    if(appName)
      setInterval(function () {
        console.log('ping every 20 minutes');
    	  request.get('http://' + appName + '.herokuapp.com/ping');
      }, 20 * 60 * 1000);
  
  });
  
  var mathParser = new math.parser();
  
  handlers.setMathParser(mathParser);
  
  app.get('/eval', handlers.evalGet);
  app.post('/eval', handlers.evalPost);
  
  app.get('/scope/read', handlers.scopeReadGet);
  
  app.get('/ping', function(req, resp) {
    resp.send('pong');
  });
  
subject: add ping itself