Add Referrer-Policy as a default response header

[jpb]

https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-header

[codecov-io]

Codecov Report

Merging #87 into master will not change coverage. The diff coverage is 100%.

@@            Coverage Diff            @@
##             master      #87   +/-   ##
=========================================
  Coverage     82.19%   82.19%           
  Complexity      954      954           
=========================================
  Files            86       86           
  Lines          2556     2556           
  Branches        332      332           
=========================================
  Hits           2101     2101           
  Misses          334      334           
  Partials        121      121

Impacted Files	Coverage Δ	Complexity Δ
...in/java/guru/nidi/ramltester/core/RamlChecker.java	94.18% <100%> (ø)	48 <0> (ø)	:arrow_down:

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