Remove Process.fork tests, untag core/process/fork_spec
Revert deletion of our Process.fork tests
Implement basic Array#map!
Merge pull request #425 from jstepien/fork-specs-pass

Remove Process.fork tests, untag core/process/fork_spec
Array#map! modifies the array in place
All Array#last examples pass
All Array#length examples pass
Merge pull request #432 from jstepien/array-length

All Array#length examples pass
Merge pull request #431 from jstepien/array-last

All Array#last examples pass
Merge pull request #429 from jstepien/array-map-bang

Implement basic Array#map!
We pass all pop specs.