Updated nokogiri to fix vulnerability scan failures (#400)

* Updated nokogiri due to vulnerability scan failures: CVE-2016-4658, CVE-2019-11068 and CVE-2019-5477.

* Updated to support most recent version

CHANGELOG.md

@@ -1,5 +1,5 @@
 ## master (unreleased)
-  - 
+  - Update awsome_print.gemspec nokogiri dependency to resolve CVEs [@gvwirth]
 
 ## 1.9.0
   - Update method signature after change in IRB [@febeling]

awesome_print.gemspec

@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'appraisal'
   s.add_development_dependency 'fakefs', '>= 0.2.1'
   s.add_development_dependency 'sqlite3'
-  s.add_development_dependency 'nokogiri', '>= 1.6.5'
+  s.add_development_dependency 'nokogiri', '>= 1.11.0'
   # s.add_development_dependency 'simplecov'
   # s.add_development_dependency 'codeclimate-test-reporter'
 end