Retire scitools.org.uk

[trexfeathers]

Enabled by:

• Move the documentation to ReadTheDocs? cartopy#1765
• Organisational README .github#199

Once both the above are completed, there will be no need for the website in addition. The URL has been used in many places for many years, so should remain 'up', but should simply redirect to the README being prepared in SciTools/.github#199.

Benefits:

• Simplified maintenance of SciTools
• Less confusion - it can sometimes be hard to remember to keep the website up to date
• A 'landing page' in the place that modern OSS developers expect it - within the GitHub organisation

[tkknight]

For reference, we have redirects for Iris docs already, suggest the same approach may be used.

https://github.com/SciTools/scitools.org.uk/blob/master/iris/index.html