Check if current_user exists in template

Fixes #4

{{cookiecutter.app_name}}/{{cookiecutter.app_name}}/templates/nav.html

@@ -22,7 +22,7 @@
       <li><a href="{{ url_for('public.home') }}">Home</a></li>
       <li><a href="{{ url_for('public.about') }}">About</a></li>
     </ul>
-    {% if current_user.is_authenticated() %}
+    {% if current_user and current_user.is_authenticated() %}
     <ul class="nav navbar-nav navbar-right">
         <li>
             <p class="navbar-text"><a class="navbar-link" href="{{ url_for('user.members') }}">Logged in as {{ current_user.username }}</a></p>

{{cookiecutter.app_name}}/{{cookiecutter.app_name}}/tests/webtest_tests.py

@@ -30,6 +30,22 @@ class TestLoggingIn(DbTestCase):
         res = form.submit().maybe_follow()
         assert_equal(res.status_code, 200)
 
+    def _login(self, username, password):
+        res = self.w.get("/")
+        # Fills out login form in navbar
+        form = res.forms['loginForm']
+        form['username'] = username
+        form['password'] = password
+        # Submits
+        res = form.submit().maybe_follow()
+        return res
+
+    def test_sees_alert_on_log_out(self):
+        res = self._login(self.user.username, 'myprecious')
+        res = self.w.get(url_for('public.logout')).maybe_follow()
+        # sees alert
+        assert_in('You are logged out.', res)
+
     def test_sees_error_message_if_password_is_incorrect(self):
         # Goes to homepage
         res = self.w.get("/")