Search for gradient definition inside CSS property value
function findGradient(cssProp) {
		var value = cssProp.value();
		var gradient = null;
		var matchedPart = _.find(cssProp.valueParts(), function(part) {
			return gradient = module.parse(part.substring(value));
		});
		
		if (matchedPart && gradient) {
			return {
				gradient: gradient,
				valueRange: matchedPart
			};
		}
		
		return null;
	}