make is_active, is_authenticated, and is_anonymous properties on the Anonymous class so that the login_required decorator will work correctly and disable anonymous browsing

cps/templates/detail.html

@@ -42,7 +42,7 @@
             {% if g.user.kindle_mail and g.user.is_authenticated %}
             <a href="{{url_for('send_to_kindle', book_id=entry.id)}}" id="sendbtn" class="btn btn-primary" role="button"><span class="glyphicon glyphicon-send"></span> {{_('Send to Kindle')}}</a>
             {% endif %}
-          {% if (g.user.role_download() and g.user.is_anonymous()) or g.user.is_authenticated %}
+          {% if (g.user.role_download() and g.user.is_anonymous) or g.user.is_authenticated %}
               <div class="btn-group" role="group">
                 <button id="read-in-browser" type="button" class="btn btn-primary dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                   <span class="glyphicon glyphicon-eye-open"></span> {{_('Read in browser')}}
@@ -157,7 +157,7 @@
         </p>
         </div>
       {% endif %}
-      {% if not g.user.is_anonymous() %}
+      {% if not g.user.is_anonymous %}
 
         <div class="custom_columns">
           <p>