Updated Icelandic post code field

[HenrikOssipoff]

It seems like there were missing a lot of Icelandic post codes. It also appears that the list contained a lot of post codes that are actually not valid post codes.

The list have been updated based on the official data bank from Postur.is: https://www.postur.is/en/about-us/post-offices/post-codes/data-files/

I'm not sure if this is actually a valid change, given that this removes some post codes? Should the new ones just be added, and the old ones kept?

Also note that some cities have seemingly changed names based on the newest data.

All Changes

• Add an entry to the docs/changelog.rst describing the change.

• Add an entry for your name in the docs/authors.rst file if it's not
  already there.

[benkonrath]

Thanks for the PR and sorry for the delay. The next release will be 3.0 which can have breaking changes. The timing of this fix is good but we also have to consider this even if we're weren't doing a major version bump - we'd just have to include in a different way.

The PR looks good. The only addition would be specifically mentioning the breaking change as a new line under the notice for the removal of the checksum functions. Thanks.

[HenrikOssipoff]

@benkonrath Thanks for the review. I've added a notice and re-worded the change log slightly. Let me know if it's good, and I'll squash the PR.

[codecov-io]

Codecov Report

Merging #394 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #394      +/-   ##
==========================================
- Coverage   95.87%   95.85%   -0.02%     
==========================================
  Files         162      162              
  Lines        4004     3985      -19     
  Branches      532      532              
==========================================
- Hits         3839     3820      -19     
  Misses         99       99              
  Partials       66       66

Impacted Files	Coverage Δ
localflavor/is_/is_postalcodes.py	100% <ø> (ø)	⬆️
localflavor/id_/forms.py	91.3% <0%> (-0.08%)	⬇️
localflavor/ee/forms.py	96.61% <0%> (-0.06%)	⬇️
localflavor/generic/validators.py	100% <0%> (ø)	⬆️
localflavor/md/validators.py	100% <0%> (ø)	⬆️
localflavor/pt/forms.py	100% <0%> (ø)	⬆️
localflavor/lv/forms.py	100% <0%> (ø)	⬆️
localflavor/id_/id_choices.py	100% <0%> (ø)	⬆️
localflavor/bg/validators.py	100% <0%> (ø)	⬆️

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[benkonrath]

Looks good. Just that issue with the hanging text in the changelog needs to be sorted out. Thanks.