changed struct tag from wrp to json

[kcajmagic]

Closes #39

[codecov-io]

Codecov Report

Merging #42 into master will not change coverage.
The diff coverage is 38.46%.

@@          Coverage Diff           @@
##           master     #42   +/-   ##
======================================
  Coverage    47.3%   47.3%           
======================================
  Files          15      15           
  Lines        3097    3097           
======================================
  Hits         1465    1465           
  Misses       1473    1473           
  Partials      159     159

Impacted Files	Coverage Δ
messages.go	96.61% <ø> (ø)	⬆️
format.go	70.91% <ø> (ø)	⬆️
messages_codec.go	35.47% <38.46%> (ø)	⬆️

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