Add information on gitter channel to the docs

[piotr-dobrogost]

I found out there's gitter channel from issue #2087 looking for information on IRC channel.

[oliviertassinari]

There is a badge here https://github.com/callemall/material-ui/blob/master/README.md for the gitter channel.

[alitaheri]

@oliviertassinari not in the docs site there isn't.

[oliviertassinari]

not in the docs site there isn't.

That's a good point.

[Zadielerick]

Would it be ok to add it in the getting started page? Maybe under Prerequisites or as a new "Help" menu Item?

[alitaheri]

How about the main page?

Want to help make this project awesome? Check out our repo.

and then a Join the chat [ gitter badge ] ?

[Zadielerick]

@subjectix That would also work, So right underneath it or side by side?

[alitaheri]

@Zadielerick I'm still wondering which is better myself 😅 @oliviertassinari What do you think?

[oliviertassinari]

What about having a Community section?
Something like http://getbootstrap.com/getting-started/#community.

[Zadielerick]

@oliviertassinari 👍

[alitaheri]

@oliviertassinari great idea 👍 👍

[oliviertassinari]

@Zadielerick Do you want to take the lead on this?

[alitaheri]

@oliviertassinari Flip a coin? 😁 😁 😁

[oliviertassinari]

Toss 🎲

[alitaheri]

@oliviertassinari I don't have a dice with me 😁 I go Tails, flip a coin. :D

[oliviertassinari]

Alright, I'm gonna do it!

[alitaheri]

@oliviertassinari Thanks a lot, 👍 👍 👍