Add "Unreleased" section to the changelog

[mehlah]

I'm writing a changelog in preparation for the next 1.0.0 release. (issue #1667)
I dumped the commit log (~300 commits) then worked it out commit by commit to keep only relevant ones and match the previous changelog format.
As you can see I still have a couple PRs to process before finishing it.
I'll go through it another time to make the sentences better with clarifications, double check breaking changes and reorder some items.

Am I on the right track? Do you have any feedbacks to make it better?

I tried to be consistent with what have been done before but I think we can make it better by:

• Renaming History.md ~> Changelog.md, which is more conventional. (note that it was named Changelog before but renamed to History.txt by 41e951a)
• Link to PRs or issues when is relevant for more details
• Group changes in sections "Added", "Fixed", "Deprecated", ...
• Maintain an "Unreleased" section and update it regularly (ideally for each PR merged) to avoid writing the changelog for a whole year of work and minimize the effort required for new releases.

Any thoughts on this?

[thomasfedb]

I'd suggest CHANGELOG.md rather than Changelog.md in like with the README.md and CONTRIBUTING.md files we have. Arguably we should move CONTRIBUTING.md into the wiki...

[tmaier]

I like the change log format defined at http://keepachangelog.com.

It uses, like you do "added", "fixed" and "deprecated", but groups them. I find good to get a better understanding what changed without using CMD+F to highlight all deprecated/removed things

[thomasfedb]

That's a nice format @tmaier, I like it too.

I like the header also:

# Change Log
All notable changes to this project will be documented in this file.
This project adheres to [Semantic Versioning](http://semver.org/).

I feel that we should definitely look to adopt SemVer when we release 1.0.0.

[thomasfedb]

When complete this will resolve #1667.

[mehlah]

@thomasfedb I updated the changelog 📝 based on your feedbacks and some of my suggestions above.
Please let me now if this looks good for you.

[thomasfedb]

That's looking fantastic @mehlah, although I'm inclined to suggest that we should include as much history as possible - although the 0.10.0 cut-off may in fact be reasonable.

The only other thing missing might be issue/PR references. What do you think?

[mehlah]

@thomasfedb

The only other thing missing might be issue/PR references. What do you think?

Booya! ded0237