se-customizer-controls.php

<?php
if( class_exists( 'WP_Customize_Control' ) ) {
	class WP_Customize_Range extends WP_Customize_Control {
		public $type = 'range';

        public function __construct( $manager, $id, $args = array() ) {
            parent::__construct( $manager, $id, $args );
            $defaults = array(
                'min' => 0,
                'max' => 10,
                'step' => 1
            );
            $args = wp_parse_args( $args, $defaults );

            $this->min = $args['min'];
            $this->max = $args['max'];
            $this->step = $args['step'];
        }

		public function render_content() {
		?>
		<label>
			<span class="customize-control-title"><?php echo esc_html( $this->label ); ?></span>
			<input class='range-slider' min="<?php echo $this->min ?>" max="<?php echo $this->max ?>" step="<?php echo $this->step ?>" type='range' <?php $this->link(); ?> value="<?php echo esc_attr( $this->value() ); ?>" oninput="jQuery(this).next('input').val( jQuery(this).val() )">
            <input onKeyUp="jQuery(this).prev('input').val( jQuery(this).val() )" type='text' value='<?php echo esc_attr( $this->value() ); ?>'>

		</label>
		<?php
		}
	}
}

?>