fix(expand): parameters & responses should properly follow remote doc resolution when SKipSchema

[fredbi]

• fixes Expander: when expanding with SkipSchema, the relative path is lost #182
• contributes Flatten stopped processing nested directories in v0.26.0 go-swagger/go-swagger#2743

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (b445199) 64.78% compared to head (0bf0cbc) 65.43%.

Files	Patch %	Lines
expander.go	75.00%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #183      +/-   ##
==========================================
+ Coverage   64.78%   65.43%   +0.65%     
==========================================
  Files          29       29              
  Lines        2845     2844       -1     
==========================================
+ Hits         1843     1861      +18     
+ Misses        833      820      -13     
+ Partials      169      163       -6     

Flag	Coverage Δ
oldstable	65.43% <75.00%> (+0.65%)	⬆️
stable	65.43% <75.00%> (+0.65%)	⬆️

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[fredbi]

@casualjim @youyuanwu

Added PRs with additional testing in known repos using this feature:

• test(flatten): asserts that the ExpandSpec fix in spec works analysis#93 (draft, based on tag on my fork)
• chore: updated dependencies for examples go-swagger/go-swagger#3057 (draft, same remark)

Seems to work, even if tinkering with this part has always been a bit dodgy...