[dev] Adde dns-zone to Gemfile

Gemfile

@@ -6,3 +6,4 @@ gem "diffy"
 gem "mediawiki_api"
 gem "net-ssh"
 gem "ruby-ip"
+gem 'dns-zone'

Gemfile.lock

@@ -2,6 +2,7 @@ GEM
   remote: https://rubygems.org/
   specs:
     diffy (3.2.0)
+    dns-zone (0.3.1)
     domain_name (0.5.20170223)
       unf (>= 0.0.5, < 1.0.0)
     faraday (0.11.0)
@@ -31,6 +32,7 @@ PLATFORMS
 
 DEPENDENCIES
   diffy
+  dns-zone
   hash_validator
   hashdiff
   mediawiki_api