Add Jekyll tag to isolate "production-only" doc components.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #56 from pwendell/jekyll-prod and squashes the following commits:

1bdc3a8 [Patrick Wendell] Add Jekyll tag to isolate "production-only" doc components.

1 files changed, 14 insertions, 0 deletions

diff --git a/docs/_plugins/production_tag.rb b/docs/_plugins/production_tag.rb
new file mode 100644
index 0000000000..9f870cf213
--- /dev/null
+++ b/docs/_plugins/production_tag.rb
@@ -0,0 +1,14 @@
+module Jekyll
+  class ProductionTag < Liquid::Block
+
+    def initialize(tag_name, markup, tokens)
+      super
+    end
+
+    def render(context)
+      if ENV['PRODUCTION'] then super else "" end
+    end
+  end
+end
+
+Liquid::Template.register_tag('production', Jekyll::ProductionTag)