Added option to disable/enable html escape on json marshal

[jeevatkm]

For #177

[codecov]

Codecov Report

Merging #179 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
+ Coverage   96.24%   96.31%   +0.07%     
==========================================
  Files           9        9              
  Lines        1065     1086      +21     
==========================================
+ Hits         1025     1046      +21     
  Misses         22       22              
  Partials       18       18

Impacted Files	Coverage Δ
middleware.go	91.73% <100%> (ø)	⬆️
client.go	97.02% <100%> (+0.04%)	⬆️
request.go	100% <100%> (ø)	⬆️
util.go	92% <100%> (+0.4%)	⬆️
default.go	100% <100%> (ø)	⬆️
request17.go	100% <100%> (ø)	⬆️

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