Add total count for group by searchable_type example

[fagiani]

Hello @nertzy

It took me a couple of hours to figure how to do a composite count for each searchable_type it and as I see some issues relating count I thought this example would eventually become handy to other folks in the future.

As you encouraged in #180 (here), I am sending this pull request as it is probably going to clarify both count and group scenarios in one place.

Hope it helps!

[fagiani]

@nertzy

Got the opportunity to add yet another example based on the issue #53 (here)

Just trying to make it easier for the new users.

Keep Rocking!

[nertzy]

Thanks!