make acceptsGzip public about gziphandler

[jprobinson]

I think this has popped up a few times so I'm into adding the option to alter the default.

Instead of making that func public, perhaps we can add a func AcceptsGzip(func(*http.Request) bool) option to let folks optionally extend it?

Would that fit your use case?

[meirf]

That is a slick api addition and I could see it being useful to others, but I don't have an issue with the way the library is determining compression. I just want to access the logic independently.

Feel free to change the title of this issue/repurpose/close for AcceptsGzip.

[adammck]

This is a dupe of #34 and #48, and I think the same recommendation applies. I don't see any problem with exporting the func, but there's already a better implementation in gddo.

[tmthrgd]

@meirf I have an implementation based on gddo available at tmthrgd/httputils if that's useful to you.