code: function top(array) {
      return topTask;
  
      function topTask() {
        var value = array[array.length - 1];
        return resolve(value);
      }
    }
docs: creates a promise-returning function which inspects the last value on the array.
  
  @class promisen
  @static
  @function push
  @param array {Array|Array-like}
  @returns {Function} promise-returning function
  @example
  var promisen = require("promisen");
  
  var stack = ["foo", "bar"]; // stack is an array
  
  var task2 = promisen(promisen.top(stack), task1);
  
  task2().then(function() {...}); // stack.length == 2