Redo all our callouts with the custom callout plugin

- Replaces manual use of .bd-callout with {% callout [type] %}
- Rearranged some callouts for proximity to others
- Turned long lists of callouts--like those on tooltips, plugings, etc--into a list because holy shit that's overwhelming

docs/_plugins/callout.rb

@@ -0,0 +1,29 @@
+# Source: http://stackoverflow.com/questions/19169849/how-to-get-markdown-processed-content-in-jekyll-tag-plugin
+
+module Jekyll
+  module Tags
+    class CalloutTag < Liquid::Block
+
+      def initialize(tag_name, type, tokens)
+        super
+        @type = type
+        if type == "danger"
+          @type = "danger"
+        elsif type == "warning"
+          @type = "warning"
+        elsif type == "info"
+          @type = "info"
+        end
+      end
+
+      def render(context)
+        site = context.registers[:site]
+        converter = site.getConverterImpl(::Jekyll::Converters::Markdown)
+        output = converter.convert(super(context))
+        "<div class=\"bd-callout bd-callout-#{@type}\">#{output}</div>"
+      end
+    end
+  end
+end
+
+Liquid::Template.register_tag('callout', Jekyll::Tags::CalloutTag)