#98 Bug/incorrect response code for empty body

[jschulte-maxmine]

This resolves an issue where if the route is not found the gzip lib returns 200 status code if nothing writes to the body.

I considered a couple of approaches:

• Conditionally write the headers during the defer, this overrides the default Gin behaviour which is not desirable
  • This has a bunch of edge cases like if another middleware is doing something with 404 bodies
• Conditionally ignore the gzip middleware on 404 status codes or set to do not compress
  • If there is response content by another middleware theres no reason why we can't compress it
• Conditionally replace the gzip writer with the original gin writer if it hasn't already been used
• Seemed to be the most sensible if we are not going to use the gzip writer we can just put the gin writer back in