Search for nearest comment in <code>str</code>, starting from index <code>from</code>
@param {String} text Where to search
@param {Number} from Search start index
@param {String} start_token Comment start string
@param {String} end_token Comment end string
@return {Range} Returns null if comment wasn't found
function searchComment(text, from, startToken, endToken) {
		var commentStart = -1;
		var commentEnd = -1;
		
		var hasMatch = function(str, start) {
			return text.substr(start, str.length) == str;
		};
			
		// search for comment start
		while (from--) {
			if (hasMatch(startToken, from)) {
				commentStart = from;
				break;
			}
		}
		
		if (commentStart != -1) {
			// search for comment end
			from = commentStart;
			var contentLen = text.length;
			while (contentLen >= from++) {
				if (hasMatch(endToken, from)) {
					commentEnd = from + endToken.length;
					break;
				}
			}
		}
		
		return (commentStart != -1 && commentEnd != -1) 
			? require('range').create(commentStart, commentEnd - commentStart) 
			: null;
	}