Add google analytics code

[mauricioaniche]

The JS code is in the base.html. We need only the GA code. I have one, just need to confirm.

[mauricioaniche]

@jurgenvinju can you take a look at google analytics and confirm that data is coming in? If so, feel free to close this issue.

[jurgenvinju]

it's in a transitional phase I guess. Let's have a look tomorrow again.