add __contains__() for widgets.COLORS and widgets.WIDGET_TYPES
add __contains__() for widgets.COLORS and widgets.WIDGET_TYPES

StephenPCG/django-adminlte-templates,xmyth/django-adminlte-templates,StephenPCG/django-adminlte-templates,xmyth/django-adminlte-templates,xmyth/django-adminlte-templates,StephenPCG/django-adminlte-templates