php55-redis: require igbinary by default (follow RHEL), expand config file sample
php55-redis: require igbinary by default (follow RHEL), expand config file sample

Closes #1606.

Signed-off-by: Alan Ivey <ee249fd9166eccef852f50ca0cbb6ff8665afe99@gmail.com>

dguyon/homebrew-php,ablyler/homebrew-php,mkalkbrenner/homebrew-php,philcook/homebrew-php,TomK/homebrew-php