Add Analytics module (Django app)

[Wgoeh]

Start a new apps.analytics app to basically track user interaction with the system.
This will:

• track likes and favourites (products)
• track user shopping cart

[julienho-ops]

I will start on Saturday. If someone can start before, then he can do it.

[Wgoeh]

I think we don't need it yet, we can focus on improving other features that can be showcased at the PyCon Event.