when you use `CMD ["/usr/local/bin/polkadot"]` in dockerfile, you don’t need to use `polkadot` while creating a container.

* Update docker.md

Few Edits:
 - Use the `latest` version of polkadot.
 - Add a missing `--` when reporting the version.

* Update docker.md use `westend` chain

> Alex doesn't exist anymore, the current test net is `westend`.
According to https://github.com/paritytech/polkadot/issues/803

Connect rpc port 9933 failed if polkadot startup without --rpc-external

Ross Bulat authored Mar 29, 2019 and asynchronous rob committed Mar 29, 2019

Document Limiting Resources for Docker Containers

* update version to 0.3.14 and add --chain alex

- update to latest docker polkadot version - 0.3.14
- add the `--chain alex` argument which is necessary for the Alexander testnet

* add custom node name

add custom node name

* docs: Update Readme for PoC-3

* docs: Fix formatting and update Docker section

* docs: Fix formatting. Start trying to make consistent with Substrate repo

* docs: Move Two-Node example into Hack on Substrate