zero.Init() clarification (#880)
* zero.Init() clarification
clarify that if `model.half()` can't fit into gpu memory `zero.Init()` is a must.
this proposal is via @samyam's clarification shared elsewhere.
Thank you.
* style
* add clarity
* style
Co-authored-by: Olatunji Ruwase <olruwase@microsoft.com>
