Skip header value matching if entry is empty slice (didip#104)

* Skip header value matching if entry is empty slice

* Test function name tweak

* Fix race cond for test by atomic int & sync map

* Fix test build error

Repleace atomic.Int64 and sync.Map with a naive map with mutex lock.
Doing so because the build tool is at go version 1.14,
while atomic.Int64 is introduced at go 1.19 I think.

* Shorten test function name to pass ci lint

* Simplify test case to pass cyclomatic complexity constraint

move to v7

Block by IPv6 /64 rather than individual address (didip#98)

Merged. Thank you!

Add option for rate-limiting ignoring the URL path (didip#72)

Issue91 (didip#93)

* attempt to refactor and fix issue91

* We need a skip limiter function before rate limiting.

* add more ShouldSkipLimiter

* Finish up ShouldSkipLimiter

* fix linter

fix didip#92

add ability to send back something other than the default (didip#89)

* add ability to send back something other than the default message and code

* add comment to exported methods

bump tollbooth internal references to v6, go mod tidy (didip#87)

Update to version v6.0.0

Fix test for issue didip#48