Use writeCapture to embed gists to Tumblr

gistembed.js

$(document).ready(function() {
    var prefix = "https://gist.github.com/";
    $('a[href^="' + prefix + '"]').each(function(i) {
        var $anchor = $(this),
            $el = $("<p></p>");
        $anchor.replaceWith($el);
        writeCapture.html($el, '<script src="'+$anchor.text()+'.js"></scr' + 'ipt>');
        $anchor.remove();
    }); 
});