Add `yarn deploy` on Travis CI instructions.

[tsuberim]

Is this a bug report?

No.

I'm trying to automatically deploy to gh-pages from travis.
Getting this error:

$ gh-pages -d build
remote: Invalid username or password.

Would be great to add instructions on how to integrate this with travis (maybe do some magic by detecting CI=true).

[lhuria94]

Specific to your issue:

I think it could be related to this: mozilla/oghliner#91
Or provide some more info/your repo.

[Timer]

Hi! If you get this working feel free to send a PR to us to update the docs for future people, but we don't have the bandwidth to handle this right now.

Thanks!