Upgrades tabstops in output node in order to prevent naming conflicts
@param {AbbreviationNode} node
@param {Number} offset Tab index offset
@returns {Number} Maximum tabstop index in element
function(node, offset) {
			var maxNum = 0;
			var options = {
				tabstop: function(data) {
					var group = parseInt(data.group);
					if (group > maxNum) maxNum = group;
						
					if (data.placeholder)
						return '${' + (group + offset) + ':' + data.placeholder + '}';
					else
						return '${' + (group + offset) + '}';
				}
			};
			
			_.each(['start', 'end', 'content'], function(p) {
				node[p] = this.processText(node[p], options);
			}, this);
			
			return maxNum;
		}