after :all + around :all

[grosser]

for after :all:
we need to track some kind of class hierarchy since a sub-class should not trigger the patent-class to run it's after :all hook

describe a do
  after :all { foo }
  it foo
  # not here
  describe b do
    it bar
    # but here
  end
end

especially with random test (can be disabled) + random class ordering (cannot be disabled without hackery) that will be tricky
also the usefulness is pretty low since there could be lots of tests that don't belong to the class with after :all that are run in between

for around :all:
once after :all works that should be the same fiber hackery like we use for the current around