How do I get masonry to run again once twitter widgets have rendered?
I went through the twitter documentation and found a way to call functions on twitter widget events:

// Load the twitter widgets script
window.twttr = (function(d, s, id) {
  var js, fjs = d.getElementsByTagName(s)[0],
    t = window.twttr || {};
  if (d.getElementById(id)) return t;
  js = d.createElement(s);
  js.id = id;
  js.src = "https://platform.twitter.com/widgets.js";
  fjs.parentNode.insertBefore(js, fjs);

  t._e = [];
  t.ready = function(f) {
    t._e.push(f);
  };

  return t;
}(document, "script", "twitter-wjs"));

// Bind an event to rerun the masonry layout when a tweet is rendered
twttr.ready(
  function (twttr) {
    twttr.events.bind(
      'rendered',
      function (event) {
        jQuery(function($) {
          $('.view-content.masonry').masonry();
        });
      }
    );
  }
);