Documentation for declared

[myitcv]

I've just discovered (via the tests) declared(params). Awesome.

But it's not anywhere in the docs, README.md or the wiki.

I'm happy to raise a pull request for README.md, but before I do is there an easier way (read: wiki) for documenting these hidden gems that you would prefer?

Thanks

[dblock]

Please do make a PR into the README. Thanks!

[myitcv]

Sure will... can you comment on #503 before I do?