gistfile1.txt

@janisz I did a small investigation today at morning. 
We can create `AliasedHash` which implements `Hash` interface:
```
type AliasedHash struct {
	aliases *sync.Map
}

func NewAliasedHash() AliasedHash {
	return AliasedHash{
		aliases: &sync.Map{},
	}
}

func (h AliasedHash) AddAlias(key, value string) {
	h.aliases.Store(key, value)
}

func (h AliasedHash) Sum64(key string) uint64 {
	value, ok := h.aliases.Load(key)
	if ok {
		key = value.(string)
	}
	var hash uint64 = offset64
	for i := 0; i < len(key); i++ {
		hash ^= uint64(key[i])
		hash *= prime64
	}
	return hash
}
```
But it will fall with this test:
```
func TestAliasedHash(t *testing.T) {
	h := NewAliasedHash()
	cfg := DefaultConfig(5 * time.Second)
	cfg.Hasher = h
	cache, _ := NewBigCache(cfg)

	h.AddAlias("key_1", "key_2")

	cache.Set("key_1", []byte("value"))
	cache.Set("key_2", []byte("value"))

	if _, err := cache.Get("key_1"); err != nil {
		t.Fatal(err) // fails here
	}
	if _, err := cache.Get("key_2"); err != nil {
		t.Fatal(err)
	}
}
```

The problem is here:`shard.go:44` 'cause we're comparing given key & stored key
```
if entryKey := readKeyFromEntry(wrappedEntry); key != entryKey {
```
There is no possibility(right now) to change a key after a hashing function.