Added mysqlnd and opcache modules.
adjusted opcache package name for amazon
Adding test for cookbook inhertance. Updating to use serverspec_helper.
Merge remote-tracking branch 'origin/mysqlnd_and_opcache_for_php55' into inheritance-fix
Refactoring attributes to fix issue with cookbook inheritance.

Can't compute values based on node['jr-php'] because wrapper cookbook default attributes aren't set on node['jr-php'] until after this cookbook's attribute files are loaded. Which means that the previous switch case on node['jr-php']['php_version'] would only work if php version was set as normal or override at a higher precedence than cookbook.
Adding memcache recipe as alternative to memcached.
Updating mysqlnd and opcache recipes with refactor.

Adding to default extensions installed by default recipe under PHP 5.5.

Updating test for PHP 5.5.
Merge branch 'inheritance-fix'
Rubocop fixes.
Test assertions are case-sensitive, and the "Zend OPcache" output of `php -m` was throwing a false positive.
Version bump to v0.1.13