Update ref var tests

Add two new futures:
test/variables/kbrady/ref-in-tuple.future
test/variables/kbrady/ref-member.future

Retire three old futures:
test/variables/sungeun/refvar-compare-nil.future
test/variables/sungeun/refvar-no-init-with-def.future
test/variables/sungeun/refvar-no-init-with-use.future