Add automated binary releases through travis

[tizoc]

This should be enough, will try tomorrow.

[rkoeninger]

@tizoc Does that API key only work when Travis uses it or will it work when anyone uses it?

[tizoc]

@rkoeninger it is encrypted: https://docs.travis-ci.com/user/environment-variables#defining-encrypted-variables-in-travisyml

I also created a new user, gave it access to the Shen organization and generated a token with it because if you give travis an access token, it gets access to every repository you have: https://github.com/ShenBuildBot

[tizoc]

@rkoeninger btw, the way this works is that every time you push a tag, the travis build will include an extra step that will create the binary bundles. Once done it will create a new draft release and upload the files there. All you have to do is wait for it to be done and then complete the draft release and publish it.