Use a proper example host in tests
Update history for #468
Work around Zlib::GzipWriter.wrap bug in JRuby

Zlib::GzipWriter.wrap accepts options for encoding following the IO in
ruby 1.9+.

JRuby lacks support for this feature in at least 1.7.0-1.7.2, so I
worked around it using arity detection instead of Encoding detection.

See also JRuby bug #552

Works around #472