Adding usage examples.
Merge branch 'master' of github.com:rakyll/goconcurrency
Fixing coop.Every example.
Renaming coop.Die.

Die hints that fn immediately gets dead instead of waiting for a signal which
is misleading. Killable assures it's semantically wrapping a fn and waiting
for external prompt.
Make channels buffered to prevent goroutines leak.

Users may ignore done message. Also, functions which runs two goroutines that writes to one channel will always produce a leak.
Killable must send kill message if user didn't.
Merge pull request #5 from bredov/patch-1

Make channels buffered to prevent goroutines leak.
Simplfy Replicate.
Gofmt.