Added test: accepts_*_for accepts_list_for should return the correct boolean default when no value is stored
This is an accepts_value_for spec: expect values, not arrays.
Correctly return an AcceptsListFor default of `false`.

A falsey default would previously fall through to the empty list, which AcceptsValueFor would shift, returning nil. This correctly returns `[false]`, which produces the correct default in AcceptsValueFor.
Merge branch 'accepts_value_for-boolean'