Include release instructions in docs/README

[arvoelke]

After the next successful release (see #131) make sure to add the details of the release flow (since I keep forgetting), including:

• changing of version information both before and after
• changes to CHANGES.rst both before and after
• documentation requirements (Support pip install nengolib[*] #140)
• building documentation in between version changes
• PyPi commands, and the required file
• Release on GitHub including matching tag (for sphinx source-code linking)
• Add a new directory with the corresponding docs in the nengolib-docs repo
• Cleaning out dist folder and others

[arvoelke]

$ cat ~/.pypirc

[distutils]
index-servers =
  pypi

[pypi]
username=arvoelke
password=***********************

python setup.py sdist bdist_wheel
twine upload dist/*

[arvoelke]

May be affected by #175.