Tiny refactorings

While scanning the code I found some possible improvements.

WDYT?
@splattael @ricardovaleriano `#each_with_object` looks better, but..

1. It [performs](https://gist.github.com/jodosha/dac01164e08da5500b04) a little bit worse than `#each`.
2. Once the loading mechanisms will be implemented ( #25 ), I'm planning to [_"compile"_](https://gist.github.com/jodosha/dac01164e08da5500b04#file-benchmark-rb-L41) the code in order to avoid iterations at all.