Remove test files from the gem package

[orien]

There are several files in the gem package that aren't useful for downstream projects. Removing these reduces the gem package size from 83K to 50K!

gem contents diff

```diff CHANGELOG.md MIT-LICENSE README.md lib/generators/simple_form/USAGE lib/generators/simple_form/install_generator.rb lib/generators/simple_form/templates/README lib/generators/simple_form/templates/_form.html.erb lib/generators/simple_form/templates/_form.html.haml lib/generators/simple_form/templates/_form.html.slim lib/generators/simple_form/templates/config/initializers/simple_form.rb lib/generators/simple_form/templates/config/initializers/simple_form_bootstrap.rb lib/generators/simple_form/templates/config/initializers/simple_form_foundation.rb lib/generators/simple_form/templates/config/locales/simple_form.en.yml lib/simple_form.rb lib/simple_form/action_view_extensions/builder.rb lib/simple_form/action_view_extensions/form_helper.rb lib/simple_form/components.rb lib/simple_form/components/errors.rb lib/simple_form/components/hints.rb lib/simple_form/components/html5.rb lib/simple_form/components/label_input.rb lib/simple_form/components/labels.rb lib/simple_form/components/maxlength.rb lib/simple_form/components/min_max.rb lib/simple_form/components/minlength.rb lib/simple_form/components/pattern.rb lib/simple_form/components/placeholders.rb lib/simple_form/components/readonly.rb lib/simple_form/error_notification.rb lib/simple_form/form_builder.rb lib/simple_form/helpers.rb lib/simple_form/helpers/autofocus.rb lib/simple_form/helpers/disabled.rb lib/simple_form/helpers/readonly.rb lib/simple_form/helpers/required.rb lib/simple_form/helpers/validators.rb lib/simple_form/inputs.rb lib/simple_form/inputs/base.rb lib/simple_form/inputs/block_input.rb lib/simple_form/inputs/boolean_input.rb lib/simple_form/inputs/collection_check_boxes_input.rb lib/simple_form/inputs/collection_input.rb lib/simple_form/inputs/collection_radio_buttons_input.rb lib/simple_form/inputs/collection_select_input.rb lib/simple_form/inputs/color_input.rb lib/simple_form/inputs/date_time_input.rb lib/simple_form/inputs/file_input.rb lib/simple_form/inputs/grouped_collection_select_input.rb lib/simple_form/inputs/hidden_input.rb lib/simple_form/inputs/numeric_input.rb lib/simple_form/inputs/password_input.rb lib/simple_form/inputs/priority_input.rb lib/simple_form/inputs/range_input.rb lib/simple_form/inputs/rich_text_area_input.rb lib/simple_form/inputs/string_input.rb lib/simple_form/inputs/text_input.rb lib/simple_form/map_type.rb lib/simple_form/railtie.rb lib/simple_form/tags.rb lib/simple_form/version.rb lib/simple_form/wrappers.rb lib/simple_form/wrappers/builder.rb lib/simple_form/wrappers/leaf.rb lib/simple_form/wrappers/many.rb lib/simple_form/wrappers/root.rb lib/simple_form/wrappers/single.rb < test/action_view_extensions/builder_test.rb < test/action_view_extensions/form_helper_test.rb < test/components/custom_components_test.rb < test/components/label_test.rb < test/form_builder/association_test.rb < test/form_builder/button_test.rb < test/form_builder/error_notification_test.rb < test/form_builder/error_test.rb < test/form_builder/general_test.rb < test/form_builder/hint_test.rb < test/form_builder/input_field_test.rb < test/form_builder/label_test.rb < test/form_builder/wrapper_test.rb < test/generators/simple_form_generator_test.rb < test/inputs/boolean_input_test.rb < test/inputs/collection_check_boxes_input_test.rb < test/inputs/collection_radio_buttons_input_test.rb < test/inputs/collection_select_input_test.rb < test/inputs/color_input_test.rb < test/inputs/country_input_test.rb < test/inputs/datetime_input_test.rb < test/inputs/disabled_test.rb < test/inputs/discovery_test.rb < test/inputs/file_input_test.rb < test/inputs/general_test.rb < test/inputs/grouped_collection_select_input_test.rb < test/inputs/hidden_input_test.rb < test/inputs/numeric_input_test.rb < test/inputs/readonly_test.rb < test/inputs/required_test.rb < test/inputs/rich_text_area_input_test.rb < test/inputs/string_input_test.rb < test/inputs/text_input_test.rb < test/inputs/time_zone_input_test.rb < test/simple_form_test.rb < test/support/discovery_inputs.rb < test/support/misc_helpers.rb < test/support/mock_controller.rb < test/support/models.rb < test/test_helper.rb ```

[schmijos]

If someone else is reading up why this issue has not been addressed yet from Rubygems side, here's the reference: https://github.com/rubygems/rubygems/issues/735