Code review comment for lp:~rogpeppe/tomb/update-api

Reviewers: mp+96158_code.launchpad.net,

Message:
Please take a look.

Description:
As discussed on IRC:

Rename Fatal and Fatalf to Kill and Killf.

Make zero-value of Tomb good to use, and as a consequence, make Dead
and Dying into methods rather than fields.

https://code.launchpad.net/~rogpeppe/tomb/update-api/+merge/96158

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/5755055/

Affected files:
   M tomb.go
   M tomb_test.go