Made Lotus::Validation::Errors#each and #map 4x faster

```
Calculating -------------------------------------
            each blk       568 i/100ms
   each delegate blk      1978 i/100ms
-------------------------------------------------
            each blk     5746.3 (±2.5%) i/s -      28968 in   5.044358s
   each delegate blk    20033.4 (±2.6%) i/s -     100878 in   5.039105s
```

_"each blk"_ was the old algorithm, _"each delegate blk"_ is the new one.
Benchmark available at: https://gist.github.com/jodosha/df7270fbb4562027bbb8