Prompts user to input decimal, with optional default and bounds.

def decimal(self, prompt, default=None, lower=None, upper=None):
        """Prompts user to input decimal, with optional default and bounds."""
        prompt = prompt if prompt is not None else "Enter a decimal number"
        prompt += " [{0}]: ".format(default) if default is not None else ': '
        return self.input(
            curry(filter_decimal, default=default, lower=lower, upper=upper),
            prompt
        )