Adds recipe for reading Gzip-compressed files
Updates reading-gzipped-file recipe to note other stream options
Updates reading-gzipped-file recipe to add newline at end
Revises reading-gzipped-file recipe to include writing too
Renames reading-gzipped-file -> read-write-gzip
Adds newline to end of read-write-gzip
Update read-write-gzip.asciidoc

Changes "need" to "want", per standard Cookbook style
Merge #66
Add cross-references for read-write-gzip