Improve installations instructions and git branch workflow

[florentsfl]

it would be nice to improve a little bit how cqfd is installed because for now the README tells to fetch the master branch for installation, which is also used for development

Here are several solutions to that:

1. Develop on a develop branch and merge to master only for releases, it adds complexity because we shall not make pull requests to the wrong branches etc.
2. Advise in the readme to checkout to a tag (ex. v5.7.0) after cloning the repo which adds a little bit of complexity for the installation process

Which one of the solution would you prefer ? Or maybe you have other propositions ?

@gportay @deribaucourt

[gportay]

Well, if we have to choose one of the two solutions, I would vote for 2. Because 1. Is adding complexity for no good reason.

People should be aware that master branch is stable enough and it is somewhere between two releases: the actual one and the next.

I guess your making this suggestions because CQFD is not distributed by the distribution (debian, fedora, arch...), right?

I would prefer the CI to release Deb and rpm packages, and add an AUR package. I have mostly all the bits already for building arch and deb packages.

[gportay]

@florentsfl #211 211