In view of next week's stable 0.7.0 release, we have released a 0.7.0 beta version. The release consists of breaking changes that were skipped in the 0.6.x releases.
We have released a beta version so we can fix any bugs/issues that we have missed.
The minimum rust version is bumped from 1.18 to 1.22
We have also released an unstable 2018 edition on the 2018 branch