[dsl] Replace failing scenario with spec.
[form] Let field groups exist apart from forms.
Remove warning from README.
[field group] Enclose field macros in a yard group.
[field group] Don't depend on #extract_options!.
[field group] Save field names
[form] Correct param name in method documentation.
[field group] Allow querying a check box field.
[field group] Allow querying text fields.
[field group] Allow querying selects.
[field group] Test field querying.
[field group] Document .check_box.
[field group] Remove ability pass :writer option.
[field group] Document .select.
[field group] Document .text_field.
[field group] Test setting fields.
[field group] Back fields with widgets.
[field group] Support #to_table.
Bump to 0.4.0