3.0.0

Release of loky 3.0 to add DOI to the project.

See CHANGES.md for a list of change between releases.

Contributors: @tomMoral @ogrisel @pierreglaser @rth @chkoar @mgorny @aabadie @massich @albertcthomas @basnijholt @CJ-Wright @lukasz-migas @jeremiedbb