code: function push(array) {
      return pushTask;
  
      function pushTask(value) {
        Array.prototype.push.call(array, value); // copy
        return resolve(value); // through
      }
    }
docs: creates a promise-returning function which stores a value into the array.
  
  @class promisen
  @static
  @function push
  @param array {Array|Array-like}
  @returns {Function} promise-returning function
  @example
  var promisen = require("promisen");
  
  var stack = []; // stack is an array
  
  var task2 = promisen(task1, promisen.push(stack));
  
  task2().then(function() {...}); // stack.length == 2