Issue #304: pass along ordered parameter

[bdscharf]

This resolves issue #304. The ordered parameter was not being passed along to output() in one case. It is now passed, and items are popped from the front to retain the original order. Original behavior is kept in case someone needs/wants it.

Test case also added to check ordered vs. not ordered.

[codecov]

Codecov Report

Merging #326 (0a9ec62) into master (a39e06f) will decrease coverage by 0.03%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #326      +/-   ##
==========================================
- Coverage   96.81%   96.77%   -0.04%     
==========================================
  Files          20       20              
  Lines        2730     2732       +2     
==========================================
+ Hits         2643     2644       +1     
- Misses         87       88       +1     

Impacted Files	Coverage Δ
flask_restx/fields.py	96.43% <66.66%> (-0.21%)	⬇️
flask_restx/marshalling.py	98.21% <100.00%> (ø)

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[bdscharf]

Will look into resolving the coverage gap.

[j5awry]

Don't worry about the gap -- CodeCov is complaining at a unit level that ordering in fields isn't covered. However, functionally, it is covered by the test provided. If the pop didn't work, you wouldn't have the expected outcome in the test of marshalling.