Asynchronous I/O docs (#1000)
* Fix docstring
* Make screenshots clickable for easier viewing
* Navigation menu in alphabetical order; More clicable screenshots
* Rename 1Cycle doc
* Tweak naming
* Remove no longer used flag
* ZeRO3 Offload release
* Single GPU results
* Rearrange figures
* Single GPU text
* tweak intro
* zero3-offload section
* Add asynchronous i/o docs
