Add ignoreOrder check

[keepitreal]

This PR adds the ignoreOrder checks added by #166 in the master branch. I realize the optimum solution for this issue is to migrate to Webpack 2 but since I'd consider this issue fairly debilitating, I think a fix should be present for those who need something in their production environments right away and can't go through the steps to migrate.

[jsf-clabot]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #520 into webpack-1 will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           webpack-1     #520   +/-   ##
==========================================
  Coverage      80.76%   80.76%           
==========================================
  Files              4        4           
  Lines            338      338           
  Branches          71       71           
==========================================
  Hits             273      273           
  Misses            65       65

Impacted Files	Coverage Δ
index.js	80.28% <100%> (ø)	⬆️

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[alexander-akait]

@keepitreal Support legacy code (options, functions, checks, and etc) is a bad practice (we use semver to avoid accumulation this legacy stuff). I would advise you to find the time and go to webpack v2 or do fork and use this fork for own packages, where your use webpack v1. Not here. Thanks!

[michael-ciniawsky]

@bebraw @d3viant0ne We can still cut a release for v1.x? The question is if we want to take the eventual risk that this might break something in general, if not then better close the PR :)

[joshwiens]

imo, given that we are about to release 3.x the time for adding features for Webpack 1.x has come and gone.

[TheLarkInn]

Agreed.

[joshwiens]

And for reference, 1.x is already not supported in the current release version.

[joshwiens]

@keepitreal - If you need a hand getting that upgraded shoot us an @ and we'll get you squared away.