Extracts single CSS selector definition from source code
@param {String} content CSS source code
@param {Number} pos Character position where to start source code extraction
@returns {Range}
function(content, pos, isBackward) {
			var result = '';
			var len = content.length;
			var offset = pos;
			var stopChars = '{}/\\<>\n\r';
			var bracePos = -1, ch;
			
			// search left until we find rule edge
			while (offset >= 0) {
				ch = content.charAt(offset);
				if (ch == '{') {
					bracePos = offset;
					break;
				}
				else if (ch == '}' && !isBackward) {
					offset++;
					break;
				}
				
				offset--;
			}
			
			// search right for full rule set
			while (offset < len) {
				ch = content.charAt(offset);
				if (ch == '{') {
					bracePos = offset;
				} else if (ch == '}') {
					if (bracePos != -1)
						result = content.substring(bracePos, offset + 1);
					break;
				}
				
				offset++;
			}
			
			if (result) {
				// find CSS selector
				offset = bracePos - 1;
				var selector = '';
				while (offset >= 0) {
					ch = content.charAt(offset);
					if (stopChars.indexOf(ch) != -1) break;
					offset--;
				}
				
				// also trim whitespace
				selector = content.substring(offset + 1, bracePos).replace(/^[\s\n\r]+/m, '');
				return require('range').create(bracePos - selector.length, result.length + selector.length);
			}
			
			return null;
		}