Activate some todo specs that are now passing
Merge pull request #202 from xzyfer/feat/enable-passing-tests

Activate some todo specs that are now passing
Activate specs for arithmetic with lists
Merge pull request #203 from xzyfer/feat/activate-arithmetic-and-lists

Activate specs for arithmetic with lists
Add specs for issue 502
Merge pull request #204 from xzyfer/feat/activate-502

Add specs for issue 502