Fix issues with Ruby curriculum updates

* Goals that had markdown blocks now actually show up
* Fix "next_step" and "back to" to work with pages that have colons
* Prune some empty-ish pages
* Remove 'objects.step' (dupe of classes.step)

Author: tjgrathwell

lib/doc_page.rb

@@ -123,7 +123,7 @@ def body_content
       if @back
         div.back {
           text "Back to "
-          a(class: "back", href: @back) do
+          a(class: "back", href: URI.escape(@back, URI::PATTERN::RESERVED)) do
             text Titleizer.title_for_page(@back.split('#').first)
           end
         }

lib/step.rb

@@ -99,10 +99,14 @@ def link_without_toc name
     link name
   end
 
+  def _escaped str
+    URI.escape(str, URI::PATTERN::RESERVED)
+  end
+
   def simple_link name, options={}
     require 'uri'
     hash = URI.escape '#'
-    href = name + "?back=#{page_name}#{hash}step#{current_anchor_num}"
+    href = "#{_escaped(name)}?back=#{_escaped(page_name)}#{hash}step#{current_anchor_num}"
     if block_given?
       a({:href => href}.merge(options)) do
         yield

sites/en/ruby/classes.step

@@ -40,4 +40,4 @@ explanation do
   message "Data is stored on your object using **instance variables** that start with an `@` sign. Instance variables behave like normal variables, but are only visible from inside a specific instance of your object. If you want the data to be externally accessible, you have to write more methods."
 end
 
-next_step 'summary:_organizing'
+next_step 'how_to_write_a_program'