gzip middleware
embedding ResponseWriter from martini
fix issues in martini.ResponseWriter change

removed unnecessary Header func on gzipResponseWriter
added line in README.md for gzip
Merge branch 'feature/gzip' of github.com:slogsdon/martini-contrib into slogsdon-feature/gzip
Improved stability of gzip compression. Detecting content type
Merge pull request #7 from codegangsta/slogsdon-feature/gzip

Gzip Middleware
Merged with recent gzip handler