In v4.4.0, checking `defined?(ActiveSupport::Cache::MemCacheStore)`
could trigger an error loading dalli, which isn’t needed.
This fixes that bug, and prevents similar bugs by checking
`store.class.to_s` rather than `defined?(klass) && store.is_a?(klass)`.
Writing an automated test to ensure that dalli is truly optional is
difficult, but I was able to recreate the dalli load error in v4.4.0 by
running:
gem uninstall dalli
ruby -Ilib -ractive_support/all -ractive_support/cache/redis_store
-rrack/attack -e 'p Rack::Attack::StoreProxy.build(Redis::Store.new)'
Fixes#163
For throttling, when the redis client throws an exception, the request
ends up getting rate limited. Modify this to be similar to how
ActiveSupport.MemCacheStore functions (the read, write and increment
methods do not raise exceptions)