Document role of master and devel branches

[mihaic]

At this moment, GitHub reports the status of devel as: "This branch is 5 commits ahead, 7 commits behind master."

Is this intended?

[kmantel]

I think some merge commits from devel into master were not included on devel. I think we will make sure to advance devel to include these merge commits, unless you have another suggestion

[mihaic]

I have no suggestion. I do think it would be useful to write down the convention to CONTRIBUTING or a similar document for new contributors, e.g.: https://github.com/scikit-learn/scikit-learn/blob/master/CONTRIBUTING.md#how-to-contribute

[kmantel]

That's a good point. At one point we were starting to create a document for contributions, but we never completed it; we should revisit it when we can.