Upgrade `html-pipeline` gem to `2.12.2`

Gemfile

@@ -135,7 +135,7 @@ gem 'aws-sdk'
 gem 'faraday_middleware-aws-signers-v4'
 
 # Markdown and HTML processing
-gem 'html-pipeline', '~> 2.8'
+gem 'html-pipeline', '~> 2.12'
 gem 'deckar01-task_list', '2.2.1'
 gem 'gitlab-markup', '~> 1.7.0'
 gem 'github-markup', '~> 1.7.0', require: 'github/markup'

Gemfile.lock

@@ -484,7 +484,7 @@ GEM
     hipchat (1.5.2)
       httparty
       mimemagic
-    html-pipeline (2.8.4)
+    html-pipeline (2.12.2)
       activesupport (>= 2)
       nokogiri (>= 1.4)
     html2text (0.2.0)
@@ -1225,7 +1225,7 @@ DEPENDENCIES
   hashie-forbidden_attributes
   health_check (~> 2.6.0)
   hipchat (~> 1.5.0)
-  html-pipeline (~> 2.8)
+  html-pipeline (~> 2.12)
   html2text
   httparty (~> 0.16.4)
   icalendar