Update state.md

[davidmaxwaterman]

Changed lowercase 'id' to ID to match other use (in html comment).

[Raynos]

Hmm, maybe we should change all ID => id

[davidmaxwaterman]

I went with: "ID" when used in English, and 'id' when used in code, ie "ID" and id.
Either way, consistency is the key :)

[heapwolf]

probably in all docs id should be ID, either that otherwise, the reference to id should be surrounded by back-ticks or code-blocks.