ci: test Node.js 6, 8, 10 and 11

[DanielRuf]

Node.js 6, 8 and 10 are current LTS branches and 11 is stable.

See https://github.com/nodejs/Release/blob/master/README.md

Node.js 4 already reached its EOL.

[DanielRuf]

Some breaking unit tests on Node.js 11.

See https://travis-ci.org/suguru03/neo-async/jobs/451312228#L1905-L1907

  1) #detectLimit should not get item:
      AssertionError [ERR_ASSERTION]: Expected values to be strictly deep-equal:
+ actual - expected
  [
    2
+   8
+   4
-   4
-   8
  ]
      + expected - actual
       [
         2
      +  4
         8
      -  4
       ]
      
      at test/collections/test.detect.js:1152:14

[suguru03]

Thanks for the PR!
I'll look into it. 🙂

It may be a Node.js issue, I'm waiting for the response now.

[suguru03]

Related to nodejs/node#24203

[DanielRuf]

Related to nodejs/node#24203

Good to know. Let me know when there is a new patch release so I can trigger a new build.

[codecov-io]

Codecov Report

Merging #64 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #64     +/-   ##
=======================================
  Coverage     100%   100%             
=======================================
  Files           2      2             
  Lines        3316   4514   +1198     
=======================================
+ Hits         3316   4514   +1198

Impacted Files	Coverage Δ
lib/async.js	100% <0%> (ø)	⬆️

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