Time Evict LRU

This is a modification of the Vitesse LRU to include Time Based Eviction

http://code.google.com/p/vitess/source/browse/go/cache

example::

l := lruttl.NewTimeEvictLru(10000, 10*time.Minute, 1*time.Second)

l.EvictCallback = func(key string, v lruttl.Value) {
	fmt.Println("evicting ", key)
}

for i := 0; i < 100; i++ {
	istr := strconv.FormatInt(int64(i), 10)
	l.Set("key"+istr, &CacheValue{i})
}