Update html proofer

Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 gem 'github-pages', group: :jekyll_plugins
 gem 'jekyll-feed'
-gem 'html-proofer', github: 'gjtorikian/html-proofer', :ref => 'cfdaad62e2'
+gem 'html-proofer', github: 'gjtorikian/html-proofer'
 gem 'geojsonlint'
 gem 'httparty'
 gem 'jekyll-paginate'

Gemfile.lock

@@ -1,9 +1,9 @@
 GIT
   remote: git://github.com/gjtorikian/html-proofer.git
-  revision: cfdaad62e2c75a8a610fe7de56c4e1694cf7523c
-  ref: cfdaad62e2
+  revision: 65e885e193c75e735cb66efa71bab0b6404e9c23
   specs:
-    html-proofer (2.5.1)
+    html-proofer (3.0.6)
+      activesupport (~> 4.2)
       addressable (~> 2.3)
       colored (~> 1.2)
       mercenary (~> 0.3.2)
@@ -15,21 +15,23 @@ GIT
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (5.0.0.1)
-      activesupport (= 5.0.0.1)
-    activesupport (5.0.0.1)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
+    activemodel (4.2.7.1)
+      activesupport (= 4.2.7.1)
+      builder (~> 3.1)
+    activesupport (4.2.7.1)
       i18n (~> 0.7)
+      json (~> 1.7, >= 1.7.7)
       minitest (~> 5.1)
+      thread_safe (~> 0.3, >= 0.3.4)
       tzinfo (~> 1.1)
     addressable (2.3.8)
+    builder (3.2.2)
     coffee-script (2.4.1)
       coffee-script-source
       execjs
     coffee-script-source (1.10.0)
     colorator (0.1)
     colored (1.2)
-    concurrent-ruby (1.0.2)
     ethon (0.9.0)
       ffi (>= 1.3.0)
     execjs (2.7.0)
@@ -106,6 +108,7 @@ GEM
       gemoji (~> 2.0)
       html-pipeline (~> 2.2)
       jekyll (>= 3.0)
+    json (1.8.3)
     json-schema (2.5.2)
       addressable (~> 2.3.8)
     kramdown (1.11.1)