Remove redundant setup
Run full suite with :Rrunner spec or :Rrunner features

Not sure how to support Minitest here, due to its infuriating refusal to
provide a test runner binary.
Provide dispatch.vim configuration

As of this time, I'm making the somewhat arbitrary decision of
clobbering b:dispatch (which in my case, always contains generic Ruby
config) but preserving b:start (which in my case, sometimes contains
foreman start).