Automate posting to Github releases

[MartinDelille]

Here is a travis script that would enable to automatically push new release on github.

There is still some stuff you need to do to make it work because I add an encrypted personal token to enable travis to push release to my repo.

In order to make it work with your repository you must:

• Create a travis account using your Github account: https://travis-ci.org/
• Enable QLMarkdown: https://travis-ci.org/toland/qlmarkdown
• Install the command line client for Travis: brew install travis
• Create an access token with public_repo access here: https://github.com/settings/tokens/new
• Encrypt your token with the following command: travis encrypt <your-token>

It will generate a secure token that you need to replace in the script I sent to you in this PR.