ie model fields - rebase

[benkonrath]

This PR contains the code by @paulcunnane in #360 rebased to master. I started doing a review but after my investigation I had 80% of the updates done so I thought I'd just finish it.

Changes:

• Convert to using RegexField
• Remove space from regex so that it accepts Eircodes without spaces
• Add a display format with a space
• Use the the built-in strip option

@paulcunnane Could you test this version out to make sure it's working well?

Closes #360

[codecov-io]

Codecov Report

Merging #366 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #366      +/-   ##
==========================================
+ Coverage   95.97%   95.98%   +0.01%     
==========================================
  Files         158      158              
  Lines        4022     4039      +17     
  Branches      523      525       +2     
==========================================
+ Hits         3860     3877      +17     
  Misses         98       98              
  Partials       64       64

Impacted Files	Coverage Δ
localflavor/ie/forms.py	100% <100%> (ø)	⬆️

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[codecov-io]

Codecov Report

Merging #366 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #366      +/-   ##
==========================================
+ Coverage   95.95%   95.96%   +0.01%     
==========================================
  Files         160      160              
  Lines        4051     4068      +17     
  Branches      525      527       +2     
==========================================
+ Hits         3887     3904      +17     
  Misses         99       99              
  Partials       65       65

Impacted Files	Coverage Δ
localflavor/ie/forms.py	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0cbf596...0992730. Read the comment docs.

[benkonrath]

I assume this is working since the tests still pass after my changes. I'm going to merge this so that it's in the 2.2 release - we can always make changes if it needs to be adjusted for some reason.