Remove mention of 1.0.0 release from the change log.

Due to a problem where an earlier version of 1.0.0 and 1.1.0 were
published to npm and then unpublished, thereby preventing re-use of
these versions, we're going to skip straight to 1.2.0.

CHANGELOG.md

@@ -4,7 +4,7 @@ Entries in this change log follow the format suggested at http://keepachangelog.
 
 # Change Log
 
-## [1.0.0] - 2017-03-01
+## [Unreleased]
 
 ### Changed