Fix map's change (issue 105)

[matiboy]

Add simple test for change

[matiboy]

Tinkering with this PR and tests made me realize what I think is another issue:

m1 = Map.empty().add('a',1)
m2 = Map.empty().add('a',1).add('b',2)

m1 == m2 # True
m2 == m1 # False

[dbrattli]

Hi @matiboy. I didn't see your PR before I fixed the change bug. But it looks like you have found another bug as well. Anyways, I would like to keep your tests from this PR. Then we should investigate the other issue you found.

[matiboy]

Hi @matiboy. I didn't see your PR before I fixed the change bug. But it looks like you have found another bug as well. Anyways, I would like to keep your tests from this PR. Then we should investigate the other issue you found.

Hi @dbrattli Sure please feel free to copy the test into main/your own branch and close this PR, no issue.