CB-13501 : update appveyor to support node 8

[audreyso]

Platforms affected

What does this PR do?

Update appveyor to support node 8

What testing has been done on this change?

Checklist

• Reported an issue in the JIRA database
• Commit message follows the format: "CB-3232: (android) Fix bug with resolving file paths", where CB-xxxx is the JIRA ID & "android" is the platform affected.
• Added automated test coverage as appropriate for this change.

[codecov-io]

Codecov Report

Merging #414 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #414   +/-   ##
=======================================
  Coverage   43.77%   43.77%           
=======================================
  Files          17       17           
  Lines        1688     1688           
  Branches      307      307           
=======================================
  Hits          739      739           
  Misses        949      949

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