Add .pyx to setup.py compile

setup.py

@@ -89,7 +89,7 @@ def prep_pxd_py_files():
     # We also yield the py_files that have a .pxd file, as we feed these into the cythonize call.
     for root, dirs, files in os.walk(ROOT_DIR):
         for f in files:
-            if os.path.splitext(f)[1] == ".py" and f not in ignore_py_files:
+            if os.path.splitext(f)[1] in [".py", ".pyx"] and f not in ignore_py_files:
                 yield os.path.join(root, f)
             if os.path.splitext(f)[1] == ".pxd":
                 py_file = os.path.join(root, os.path.splitext(f)[0]) + ".py"