Add tljh_post_install hook

tljh/hooks.py

@@ -58,4 +58,14 @@ def tljh_config_post_install(config):
     be the serialized contents of config, so try to not
     overwrite anything the user might have explicitly set.
     """
+    pass
+
+@hookspec
+def tljh_post_install():
+    """
+    Post install script to be executed after installation
+    and after all the other hooks.
+
+    This can be arbitrary Python code.
+    """
     pass