Added config option to allow case_sensitive setting

[eusonlito]

This commit allow to config cache adapters with config settings as case_sensitive.

This feature allow to integrate cache to adapters like Dropbox (and others) that are case insensitive.

Tested on a current project that use https://github.com/spatie/flysystem-dropbox as Dropbox Adapter and this project as cache adapter.

All Cache Storage adapters allow a fourth parameter with an array of settings (currently only case_sensitive):

$cache =  new Predis(null, $config['prefix'], $config['expire'], ['case_sensitive' => false]);