Create 3-2-stable, 3-3-stable and 3-4-stable branches

[renatonitta]

In order to follow spree versions we should create more stable branches:

• 3-2-stable
• 3-3-stable
• 3-4-stable

I did an update on pt-BR locales recently: #767

I want to update again to follow the master branch on spree but if I do, it will not be compatible with 3-4-stable, the version I'm currently working on.

Other people could be working on other versions, so please create all stable branches like in spree repository.