New API

[bcardarella]

I've been bouncing the idea around in my head on a potential new API. It would look something like this:

@fixtures [:foo, :bar]
test "some test", context do
  fixtures.foo # foo's fixtures are here
  fixtures.bar # bar's fixtures are here
end

This would also allow for setting certain flag:

@fixtures :foo, virtual: true, %{ people: %{ admin: %{ name: "Thomas" } } }

In addition, when referencing other fixture files in a fixture file:

@fixtures :bar
foo model: Foo, repo:Repo do
  valid do
    bar fixtures.bar.one
  end
end