Revert "Upgrade IANA TZ Database to `2015d`."
Revert "Upgrade IANA TZ Database to `2015d`."

This reverts commit 5e6e97925f063e6d02426f4d495fbe1b7dde4d20.

Forgot to release `2015c`.

bigeasy/timezone,bigeasy/timezone,bigeasy/timezone