Fix missing URL encodings in books' links

The URL contain translated texts which are UTF-8, so they need to be
escaped properly.

app/controllers/books_controller.rb

@@ -33,7 +33,7 @@ def link
     link = params[:link]
     @book = Book.where(:code => params[:lang], :edition => params[:edition]).first
     xref = @book.xrefs.where(:name => link).first
-    return redirect_to "/book/#{@book.code}/v#{@book.edition}/#{xref.section.slug}##{xref.name}" unless @content
+    return redirect_to "/book/#{@book.code}/v#{@book.edition}/#{ERB::Util.url_encode(xref.section.slug)}##{xref.name}" unless @content
   end
 
   def section

app/models/section.rb

@@ -39,12 +39,12 @@ def prev_slug
     lang = self.book.code
     prev_number = self.number - 1
     if section = self.sections.where(:number => prev_number).first
-      return "/book/#{lang}/#{ERB::Util.url_encode(section.slug)}"
+      return "/book/#{lang}/v#{self.book.edition}/#{ERB::Util.url_encode(section.slug)}"
     else
       # find previous chapter
       if ch = self.chapter.prev
         if section = ch.last_section
-          return "/book/#{lang}/#{ERB::Util.url_encode(section.slug)}"
+          return "/book/#{lang}/v#{self.book.edition}/#{ERB::Util.url_encode(section.slug)}"
         end
       end
     end