Migrate to Vega 4

[randyzwitch]

With Vega 3 about to come out, declared bankruptcy on the majority of open issues. Develop a plan for keeping this package afloat on 0.5, 0.6 and then moving to Vega 3 before adding any additional features.

[randyzwitch]

This has been lingering so long that Vega 4 in RC2 status. Perhaps make new Vega targeting Vega 4 and only Julia 0.7/1.0