Add decorators to simplify checking for role.

biscuit/core/decorators.py

+from django.contrib.auth.decorators import user_passes_test
+
+
+def student_required(function=None):
+    actual_decorator = user_passes_test(lambda u: u.is_active and u.is_student)
+    return actual_decorator(function)
+
+
+def teacher_required(function=None):
+    actual_decorator = user_passes_test(lambda u: u.is_active and u.is_teacher)
+    return actual_decorator(function)