update pybind11 version

Author: wjakob

setup.py

@@ -106,8 +106,8 @@ def build_extensions(self):
     description='A test project using pybind11',
     long_description='',
     ext_modules=ext_modules,
-    install_requires=['pybind11>=2.3'],
-    setup_requires=['pybind11>=2.3'],
+    install_requires=['pybind11>=2.4'],
+    setup_requires=['pybind11>=2.4'],
     cmdclass={'build_ext': BuildExt},
     zip_safe=False,
 )