use '' to $eol for prevent newline at authorization header

    AnyEvent::HTTP::ScopedClient->new(
      'http://example.com',
      options => { auth => 'something' }
    );

if options->{auth} set, this module trying to encode_base64 for
`authorization` header, at this time, encode_base64 uses "\n" default
to use for line-ending-sequence.

reference - http://perldoc.perl.org/MIME/Base64.html
            encode_base64( $bytes, $eol );
use general permalink for AnyEvent Module at README
bumpup to `v0.0.5`