Bugfix support for multiple marked version constraints

What's Changed

• Upgrade everything by @bneijt in #33
• Fix issue 36 by @bneijt in #37

If we have a list of possible versions with markers on each version range, we ignore the markers. This could, very unlikely, lead to versioning issues (for example, if we have a platform marker and a multi-version constraint from a package), but the likelihood is very small.

Full Changelog: 0.5.0...0.5.1