lower the core prereq bar to 5.6.2 (the version that shipped File::Find), and promise in docs that we will stick to this
Dist::Zilla 4.300038 has a workaround for the yaml encoding issue (see rjbs/Dist-Zilla#200)
v2.027

 - promise in documentation that the generated test requires no non-core
   modules, and is compatible with perl 5.6.2
 - re-release with properly encoded META.yml