* Ensure RMM is 0.18 or later * Add use_rmm flag to global configuration * Modify XGBCachingDeviceAllocatorImpl to skip CUB when use_rmm=True * Update the demo * [CI] Pin NumPy to 1.19.4, since NumPy 1.19.5 doesn't work with latest Shap
* Ensure RMM is 0.18 or later * Add use_rmm flag to global configuration * Modify XGBCachingDeviceAllocatorImpl to skip CUB when use_rmm=True * Update the demo * [CI] Pin NumPy to 1.19.4, since NumPy 1.19.5 doesn't work with latest Shap