Some updates to the README.md

* Updated pre-reqs for 0.9.
* Fixed a couple of docker to Docker.
* Fixed the Docker build example to be correct.
* Reformatted a bunch of paragraphs

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Merge pull request #4449 from jamtur01/readme

Some fixes and 0.9.0 pre-req changes to the README.md