Memory leak fix using factories

[shuky19]

This PR fixes a memory leak found in factories, where their container was never released from its parent container, add also specs to verify the fix

The following code will leak forever in the pre-fixed-version of intravenous:

// Heavy class
function heavyMemoryClass () {
this.array = new Array(1024*10);
}
heavyMemoryClass.$inject = [];

// Container configuration
var intravenous = require('intravenous');
var container = intravenous.create();
container.register('heavyMemoryClass', heavyMemoryClass, 'unique');

// Leak reproduction
var heavyMemoryClassFactory = container.get("heavyMemoryClassFactory");
setInterval(function () {
var myClass = heavyMemoryClassFactory.get();
heavyMemoryClassFactory.dispose(myClass);
}.bind(this), 10);