Get model name for the field.

    Django 1.5 uses module_name, does not support model_name
    Django 1.6 uses module_name and model_name
    DJango 1.7 uses model_name, module_name raises RemovedInDjango18Warning

def get_model_name(model):
    """ Get model name for the field.

    Django 1.5 uses module_name, does not support model_name
    Django 1.6 uses module_name and model_name
    DJango 1.7 uses model_name, module_name raises RemovedInDjango18Warning

    """
    opts = model._meta
    if django.VERSION[:2] < (1, 7):
        model_name = opts.module_name
    else:
        model_name = opts.model_name

    return model_name