CaseInsensitiveArray rewrite for performance.
CaseInsensitiveArray rewrite for performance.

Storeing the Case-Insensitive/Sensitive Keys separately increases performance.  Also, fix for unset and valid, as well as the ability to initialize with a pre-existing Array.

zachborboa/php-curl-class,zachborboa/php-curl-class,php-curl-class/php-curl-class,thebeline/php-curl-class,php-curl-class/php-curl-class,thebeline/php-curl-class,zachborboa/php-curl-class,php-curl-class/php-curl-class