Support for JSON API Content-Type

[holmes89]

Having JSON API as a Content Type header causes the response method to compress. It should return a string.

[holmes89]

I have a solution, but am unable to push a branch for a PR.

func isTextMime(kind string) bool {
        mt, _, err := mime.ParseMediaType(kind)
        if err != nil {
                return false
        }

        if strings.HasPrefix(mt, "text/") {
                return true
	}

        switch mt {
	case "image/svg+xml":
                return true
        case "application/json":
                return true
	case "application/vnd.api+json":
                return true
	case "application/xml":
		return true
        default:
                return false
	}
}

Have a corresponding test to go along with it