Changes
** Bug
* [PHP-1425] - explain() does not raise appropriate exception for $err conditions
* [PHP-1431] - Fix database name validation to include '$external', to allow execution of user admin commands
* [PHP-1435] - MongoCollection::getIndexInfo on non-existing collection makes segmentation fault
** Improvement
* [PHP-1427] - MongoCollection::distinct() should ensure query is serialized as BSON object
* [PHP-1433] - MongoCollection::distinct() should allow array or object for query
* [PHP-1434] - MongoCollection::findAndModify() should allow array or object for query, update, and fields