New class Translator\Loader\PhpMemoryArray 

This translator loader takes a php array that already exists instead of loading it from a file like `Translator\Loader\PhpArray` does. This is beneficial when you already have the translations in memory or when using a service like Google App Engine where disk I/O is an expensive API call. It is also useful when translations come from a centralized place like memcached which is what prompted me to write this loader.