remove go-multierror lib

[theganyo]

Fixes #63

[codecov]

Codecov Report

Merging #64 (f48d7f1) into master (3355f79) will increase coverage by 1%.
The diff coverage is 84%.

@@          Coverage Diff          @@
##           master    #64   +/-   ##
=====================================
+ Coverage      84%    84%   +1%     
=====================================
  Files          27     28    +1     
  Lines        1610   1632   +22     
=====================================
+ Hits         1346   1368   +22     
  Misses        148    148           
  Partials      116    116           

Impacted Files	Coverage Δ
analytics/recovery.go	49% <0%> (ø)
analytics/staging.go	76% <0%> (ø)
analytics/record.go	87% <100%> (ø)
errorset/errorset.go	100% <100%> (ø)

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