Auto merge of #4227 - YaLTeR:version-field-fix, r=alexcrichton
authorbors <bors@rust-lang.org>
Mon, 26 Jun 2017 20:47:52 +0000 (20:47 +0000)
committerbors <bors@rust-lang.org>
Mon, 26 Jun 2017 20:47:52 +0000 (20:47 +0000)
Clarify how breaking changes should be handled before 1.0.0

Resolves #4064


Trivial merge