Pathname Objects

Web#files_path and Web#blatex_pngs_path now return Pathname objects.
Based on JHerdman's
5d1e8f420b
but requires several other changes to the code (which assumed a string).

Also, test for itex2MML 1.3.10 (you should update that too).

app/controllers/file_controller.rb

@@ -26,7 +26,7 @@ class FileController < ApplicationController
       end
     else
       # no form supplied, this is a request to download the file
-      file = @web.files_path + '/' + @file_name
+      file = @web.files_path.join(@file_name)
       if File.exists?(file)
         send_file(file)
       else
@@ -38,7 +38,7 @@ class FileController < ApplicationController
   end
   
   def blahtex_png
-    send_file(@web.blahtex_pngs_path + '/' + params['id'])
+    send_file(@web.blahtex_pngs_path.join(params['id']))
   end
     
   def delete