move away from Test::Most

Our own Import::Base is also being used, so we only need one
always use 5.10 features

We require 5.10 for recursive regex, so always enable "say" and "state"
add yto script to convert from YAML to other formats

Currently only JSON is supported, and only if the user has JSON::XS
(from CPAN) or JSON::PP (core since 5.14)
add travis config