Set up scriv for changelog management

[mdickinson]

Let's use scriv for changelog management. This is very similar to the setup that we have in TraitsUI and apptools, except that it seems better to use scriv than grow our own tool.

scriv is relatively unopinionated, flexible and easy to use; it simply lets you assemble changelog snippets in separate files under changelog.d until you're ready to collect those snippets together to assemble a changelog entry for a release. It seems like a good fit for Traits.

We're currently lacking a good place to record the information that we're expecting to use scriv for changelog management. See #1803.

xref: https://scriv.readthedocs.io/en/1.5.1/

[flongford]

Looks very useful indeed - excited to see how it works in practice

@mdickinson - is it appropriate to include the scriv package in some setup.py / etstool.py list of dependencies or shall we look into that at a later date?

[mdickinson]

@mdickinson - is it appropriate to include the scriv package in some setup.py / etstool.py list of dependencies or shall we look into that at a later date?

It's not actually needed by any of our current workflows, so I'm not sure where I'd put it. Where it should be mentioned is in developer setup instructions, but we don't have any of those. (See #1803.) It'll also impact the method of making a release, so I need to update the notes on making releases in the wiki.

[flongford]

@mdickinson - is it appropriate to include the scriv package in some setup.py / etstool.py list of dependencies or shall we look into that at a later date?

It's not actually needed by any of our current workflows, so I'm not sure where I'd put it. Where it should be mentioned is in developer setup instructions, but we don't have any of those. (See #1803.) It'll also impact the method of making a release, so I need to update the notes on making releases in the wiki.

Makes sense to me - thanks for the explanation