
TODO ist for Set::Light

* tests for $set->add(123) and $set->(1.2)
* make benchmarks (memory, time)
* implement in XS a completely own structure like:
  + strings are stored in buckets, by lenght % 8. E.g.
    + 0..3 byte strings in one bucket
    + 4..7 byte strings in another bucket
    + 8..15 byte strings in another bucket
    + 16..23 byte strings in another bucket
    + and so on
  + the bucket list is a sorted double linked list
  + insert string:  
    + search the bucket from stringlength via binary search
    + if bucket doesn't exist, create it
    + insert string into bucket (double hashed hash table?)
