Allow ability to generate changelog from multiple github milestones #48
Description
We may want to generate a changelog for multiple github milestones. Example you have 2.0.0-beta1, 2.0.0-beta2, 2.0.0-rc1 and then finally 2.0.0-stable. I want to be able to generate a changelog for the full 2.0.0-stable release and currently the only option is to move the issues from the beta, rc, etc. milestones to the 2.0.0-stable milestone.