Improve release script to prevent CI builds

[ghost]

We discussed adding the "magic CI word" in the tag message, but while
making the change, and doing some research, it does not feel totally
right. I think we should just fix the message of the commit we're
tagging this is the one that should skip CI, and hopefully it will
also apply to the tag.
Should we try this?

[thibaultdalban]

This change will remove the ability to let the CI deploy the application.
Skip the CI just for the tag build is the best option, but maybe it's not possible.

[ghost]

This change will remove the ability to let the CI deploy the application.

I didn't realize that at the time :/ It's fixed.

Skip the CI just for the tag build is the best option, but maybe it's not possible.

We can add the string (I updated the PR with the change on the tag
message), but it will "pollute" our tags.
Regarding codeship, I guess we need to try it to see how it will work.

[ghost]

FYI, I tried the change, and codeship will still trigger three builds
(master, develop, and the tag).