Ensure Handler::File reads all static content as bytes

Files whose mime type matches m/^text/ are assumed to be in the
appropriate encoding so they can be read as (raw) bytes and added to the
response body without having to go through an explicit decode and encode
operations. Ref #302.
Tests for utf-8 encoding of m/^text/ mime types in Handler::File.

The 1x1 transparent png was taken from
  https://commons.wikimedia.org/wiki/File:1x1.png
Do not alter PerlIO layers on file handle in read_glob_content.

Remove "binmode $fh" from read_glob_content and document that it is
the callers responsibility to set PerlIO layers on the file handle.

Also clean up whitespace and method name in synopsis POD.
Update FileUtils->read_file_content tests to include unicode chars.

Closes #302.
reflect Changes
Merge branch 'veryrusty-Pr/fileutils_utf8' into devel