Change YAML::Any to YAML

Because YAML::Any chooses backends with different behaviours, it is
flawed. YAML::XS only deals with bytes, the others deal with characters.
Switching to YAML means we are consistent.
Properly remove YAML::Any
Fix a missing pod C<>
Update POD to reflect encoding/bytes requirement
As @veryrusty suggests, make response mark itself as encoded when it
uses the serializer
reflect changes
Merge branch 'shumphrey/change-yaml-any-to-yaml'
new release: 0.13