Convert using only characters for Dist::Zilla v5

Forthcoming Dist::Zilla version 5 will manages file encodings.  Since
Pod data comes from 'content' it will be in characters, not octets, so
Pod::Text needs to turn off its encoding handling. The result can be set
back to 'content' without further modification and Dist::Zilla will
ensure the characters are properly encoded while the file is written to
disk.

This commit should not be released until after Dist::Zilla v5, but a
-TRIAL release is advised to allow users to start testing with it.

FYI: @rjbs