Support aggregation functions (min/max/sum/count/avg) (#3)

* Use generators to filter datasets

* Finish aggregation support

* .

* Bump version: 0.3.1 → 0.4.0

Merge pull request #2 from rundef/feat/indexes_support

Benchmarks and performance improvements

Merge pull request #1 from rundef/feat/indexes_support

Indexes support

Bump version: 0.2.1 → 0.2.2

Bump version: 0.2.0 → 0.2.1

Cleanup

Bump version: 0.1.0 → 0.1.1

Initial release