Add a function login template

Fix #1

flangr/templates/registration/login.html

@@ -1,4 +1,10 @@
 {% extends "base.html" %}
 
 {% block content %}
+    <h1>Login</h1>
+    <form action="" method="post">
+        {% csrf_token %}
+        {{ form }}
+        <input type="submit", value="Post">
+    </form>
 {% endblock content %}