Issue with Boolean Filters in Filterrific Gem - Incorrect Handling of "False" Values

[grantmca]

When passing a boolean value of false as a filter parameter from the controller, the gem treats it as non-present due to the .present? check performed during the define_and_assign_attr_accessors_for_each_filter method. As a result, the parameter isn't assigned to the attr_accessor and doesn't affect the filtering process. Is this the expected behavior of the gem? If not I could look into making a PR to address this