cEP metadata should include date field

[Mariatta]

Useful dates:
Date it was first authored,
Effective date,
Last update

Thoughts?

[Mariatta]

Hi, the existing cEP metadata as outlined in cEP 0:

• A cEP number.
• A Version number.
• A Title.
• The name(s) and e-mail address(es) of the Authors.
• A Status
• A Type

I'm proposing adding a date field to the list of metadata above.

While it's true we can do git blame to figure out the full history of the cEP, some dates are quite useful and should be documented as part of the cEP itself, so we can refer to it quickly.

As a comparison, official PEPs always have "Date Created" and "Post-History" dates.

[jayvdb]

Adding dates inside files which are version controlled is a bit odd, and the date will usually be 'wrong' as merges occur after authoring. Which is effective?

Maybe we could add dates to the README.md after #73 has created an index of cEPs?

[jayvdb]

So lets add dates to the pre-2018 cEPs, and see what happens during the PR. That should help us formulate which dates should be used.

[bharatpurohit97]

need some info, i guess date it was first authored should be add in date column in README.md, correct me if not.

[li-boxuan]

creation date kind of makes sense to me, because the UI on https://github.com/coala/cEPs only shows the last update time, and it would be useful if creation date is displayed so that people have a rough idea how long the cEP has been there.