Replace variables like ${var} in string
@param {String} str
@param {Object} vars Variable set (defaults to variables defined in
<code>snippets.json</code>) or variable resolver (<code>Function</code>)
@return {String}
function(str, vars) {
			vars = vars || {};
			var resolver = _.isFunction(vars) ? vars : function(str, p1) {
				return p1 in vars ? vars[p1] : null;
			};
			
			var res = require('resources');
			return require('tabStops').processText(str, {
				variable: function(data) {
					var newValue = resolver(data.token, data.name, data);
					if (newValue === null) {
						// try to find variable in resources
						newValue = res.getVariable(data.name);
					}
					
					if (newValue === null || _.isUndefined(newValue))
						// nothing found, return token itself
						newValue = data.token;
					return newValue;
				}
			});
		}