issue91 clearing session table after each test | Approach 'A'

[karliatto]

Approach A for:

• Modified tearDown function in 'test/manager.js' to clear sessions as suggested using 'express-session' module.

It is working ok like this, but I am not completely sure if the approach of using the global variable 'app'
instead of the declaring varibles below is better, so I will create other pull request with the other approach.

var session = require('express-session');
var MySQLStore = require('express-mysql-session')(session);
var sessionStore = new MySQLStore(app.config.db);