Add support for both nodejs 8 and 9

[eberhara]

No description provided.

[codecov-io]

Codecov Report

Merging #14 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #14   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines          48     48           
=====================================
  Hits           48     48

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[coveralls]

Coverage remained the same at 100.0% when pulling 02bb5b9 on add-node-8-and-9-support into 0bd45dd on master.