create examples repo about koa

[tj]

after things aren't in flux anymore +1

[tj]

actually probably better off leaving this in. "docs" commits are lame but at least people can go back and reference them easily without hunting through the wiki history

[tj]

moving examples over is probably worth it, docs i think are still useful sync'd up with master, and we can force people contributing to include doc updates in their pull-requests easier that way too

[jonathanong]

started on https://github.com/koajs/examples, but i guess you have already have a better multipart example. noticed you just closed the issue about flash messages, which i kind of added (it's just JSON, too lazy to do HTML). i can delete that if you want.

i did add a body parsing one with tests though.

[jonathanong]

https://github.com/koajs/examples