Disk-backed-map - A simple java disk backed map

A small library that provide a disk backed map implementation for storing large number of key value pairs. The map implementations (HashMap, HashTable) max out around 3-4Million keys/GB of memory for very simple key/value pairs and in most cases the limit is much lower. DiskBacked map on the other hand can store betweeen 16Million (64bit JVM) to 20Million(32bit JVM) keys/GB, regardless the size of the key/value pairs.