Upgrading yeoman-environment to 3.4.1

[scalvert]

Resolves console.warn in tests related to mismatched dependency versions between yeoman-generator and yeoman-environment.

[rwjblue]

Fails on Node 10:

FAIL test/unit/generator-test.js
  ● generators › generates the rules index file correctly

    TypeError: Object.entries(...).map(...).flat(...) is not a function or its return value is not iterable

      at Environment.getAllGenerators (node_modules/yeoman-environment/lib/environment.js:851:10)
      at Environment.getGeneratorsFeatures (node_modules/yeoman-environment/lib/generator-features.js:11:51)
      at Environment.getGeneratorsFeature (node_modules/yeoman-environment/lib/generator-features.js:24:12)
      at Environment.getGeneratorUniqueFunctionFeature (node_modules/yeoman-environment/lib/generator-features.js:38:48)
      at Environment.findGeneratorCustomCommitTask (node_modules/yeoman-environment/lib/generator-features.js:65:17)
      at runLoop.add (node_modules/yeoman-environment/lib/environment.js:1243:37)
      at Immediate.setImmediate (node_modules/grouped-queue/lib/subqueue.js:48:34)

[scalvert]

I think you previously mentioned guarding these tests. Thoughts on this?

[rwjblue]

Ya, seems fine to me

[scalvert]

OK, done. CI is just running.

[scalvert]

@rwjblue I think this is GTG.