SelectDateWidget does not support template_name argument

When used `template_name` argument to style the `SelectDateWidget` an "unexpected keyword argument 'template_name'" is shown.

The problem is easy, ´SelectDateWidget´ inherits from `forms.Widget` (from django.form) and does not include any code for reading `template_name` param.

The easiest solution while this gets solved is providing your own template with the same name as the default: "floppyforms/select_date.html" (it must be in your templates folder). That way, dajngo will get your template instead of the template provided by floppyforms.

Start with SelectDateWidget and its inheritance from forms.Widget, then inspect how the widget resolves the default floppyforms/select_date.html template. Verify that passing template_name no longer raises an unexpected-keyword error and that a custom template can still override the default.

Written by the indexing model from the issue text.