Update the install script to set up the submodule upon installation

install.py

@@ -1,8 +1,15 @@
 import contextlib
 import os
+import subprocess
 
 path = os.path.dirname(os.path.realpath(__file__))
 
+def git(*args):
+    return subprocess.check_call(["git", *list(args)])
+
+# Install Pixelization submodule
+git("submodule", "update", "--init")
+
 # we remove __init__ because it breaks BLIP - takes over the directory named models which BLIP also uses.
 with contextlib.suppress(OSError):
     os.remove(os.path.join(path, "Pixelization", "models", "__init__.py"))