Use nyc instead of instanbul

[miller45]

No description provided.

[codecov-io]

Codecov Report

Merging #175 into master will increase coverage by 28.07%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #175       +/-   ##
===========================================
+ Coverage   44.75%   72.83%   +28.07%     
===========================================
  Files           3        3               
  Lines        8282      519     -7763     
  Branches     1745        0     -1745     
===========================================
- Hits         3707      378     -3329     
+ Misses       4575      141     -4434

Impacted Files	Coverage Δ
app/util.js	92.1% <0%> (-0.21%)	⬇️
index.js
app/reporter.js	29.92% <0%> (ø)

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