Create Travis job which re-publishes the website after pushing to master

[gunnarmorling]

No description provided.

[filiphr]

I found out this from Travis. Which looks exactly what we need.

This are some of the extra properties that we can configure and my suggestions for them.

• local_dir: Directory to push to GitHub Pages, defaults to the current directory -> The public folder. Although I am not sure whether it'll work correctly with our way of building (I think it would).
• target_branch: Branch to force push to, defaults to gh-pages -> We set it explicitly to gh-pages. We can actually test I think with some other branch.
• fqdn: Optional, sets a custom domain for your website, defaults to no custom domain support. -> I think we have this already set in the repo itself
• email: Optional, comitter info, defaults to [email protected] -> Maybe we can use @mapstruct-robot
• name: Optional, comitter, defaults to Deployment Bot -> MapStruct CI Bot

[gunnarmorling]

Sounds good to me, @filiphr!