[namespaced](http://api.jquery.com/on/#event-names) events for the sendgrid-subscription widget, to prevent a race condition.

events.js

$(".sendgrid-subscription-widget").on("submit.loader", function () {
    $(this).addClass("loading")
           .append("<img src=\"my/super/cool/loading.gif\" alt=\"Loading...\">");
    $(this).find("input[type=submit").attr("disabled", "disabled");

    $(".sendgrid-subscription-widget").on("success.loader.response error.loader.response", function () {
        $(this).removeClass("loading")
        $(this).find("img").remove();
        $(this).find("input[type=submit").removeAttr("disabled");
        $(this).off(".loader.response");
    });
});