feat: switch from casbin to pycasbin

diff --git a/requirements.txt b/requirements.txt
index a5a4fbd..1a5b80a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,2 @@
-casbin>=0.8.4

+pycasbin>=2.0.0

 SQLObject>=3.8.0
\ No newline at end of file