[Meta] Documentation Improvements

[holgerd77]

I will use this issue to collect different ideas and work tasks for documentation update rounds. If you have ideas for improving the docs coming along with work on issues or PRs optimally make a note there and link to this thread.

[holgerd77]

Documentation Updates, next round:

• Note on coinbase touch simulation, see comment
• Move test set sanitation section from README to docs
• Add some Yaml test example from @hugo-dc, see EXTCODEHASH: test for deleted account #543 (comment)
• Add client installation instructions for tagged releases

[winsvega]

I think tests affected by coinbase touch simulation should be moved from state tests to blockchain
it is a blockchain logic and misleading to implement it on all state tests.

[holgerd77]

@winsvega yes, that probably makes sense. I will try to state this in the doc section that this is just the "how it currently is" and not the optimal situation and that this might change in the future.

[holgerd77]

Client installation instructions should be added to the docs as well (added the task to the list above), just had to look this up myself here again for ethereumjs-testing library update. 😛

[winsvega]

there was major documentation iprovement:
https://ethereum-tests.readthedocs.io/en/latest/