replace ConcurrentDictionary with SortedList and use a SpinLock to synchronize ( ported from https://github.com/danielcrenna/metrics-net/pull/36 by Antoine Souques
@razrin )
use consistent member prefix
port optimizations to Random next Long from (https://github.com/razrin/metrics-net/commit/1e1b9e317d5e3107c4d6bfd0a4987c329b63cb5b)