Changes
** Bug
* [PHP-382] - When 'replicaSet' option is used, authentication calls are being sent to the arbiter server
* [PHP-392] - Arbiter in the seed list acts wonky
* [PHP-869] - ReadPreference.PrimaryPreferred + Tag sets should send to primary if available
* [PHP-877] - auto gen _id clashes on heavy inserts
* [PHP-885] - Segfault on request shutdown when using save()
* [PHP-890] - PHP Driver crashes on shutdown
** Improvement
* [PHP-423] - MongoDate support for 64-bit timestamps on 32-bit systems