Make error messages visible (trac #1294).

ce4e860a introduced CSS `.alert{display:none;}` because alerts are
always included in `/signup/` and shown by JS. Use a new `.alert-hidden`
class for this purpose to avoid breaking other pages.

(imported from commit 199ba35dd3356bd4093aac2a54181331b3993ee8)

templates/zephyr/signup.html

@@ -20,18 +20,18 @@
 <div class="row-fluid shaded-background landing-page-bottom">
   <div class="content">
     <div class="span6 offset3" id="envelope-holder">
-      <div id="success" class="alert alert-success alert-block">
+      <div id="success" class="alert alert-hidden alert-success alert-block">
         <h4>Success!</h4>
         Thank you for your interest. We'll be in touch soon.
         While you wait, check out some of our <a href="/features">features</a>!
       </div>
 
-      <div id="error" class="alert alert-error alert-block">
+      <div id="error" class="alert alert-hidden alert-error alert-block">
         <h4>Ruh-roh!</h4>
         Hmmm, something went wrong. Please send email to <a href="mailto:support@humbughq.com">support@humbughq.com</a>.
       </div>
 
-      <div id="error-missing-email" class="alert alert-error alert-block">
+      <div id="error-missing-email" class="alert alert-hidden alert-error alert-block">
         <h4>Your email is required!</h4>
         How else would we be able to reach you?
       </div>

zephyr/static/js/landing-page.js

@@ -23,7 +23,7 @@ $(function () {
     $(".letter-form").ajaxForm({
         dataType: 'json', // This seems to be ignored. We still get back an xhr.
         beforeSubmit: function (arr, form, options) {
-            $(".alert").hide();
+            $(".alert-hidden").hide();
             var has_email = false;
             $.each(arr, function (idx, elt) {
                 if (elt.name === 'email' && elt.value.length) {

zephyr/static/styles/portico.css

@@ -308,6 +308,6 @@ img.screenshot{
     }
 }
 
-.alert {
+.alert-hidden {
     display: none;
 }