fix URL encoding and slash replacement

Author: Jay Parekh

lib/imagekit/url.rb

@@ -149,6 +149,13 @@ def transformation_to_str(transformation)
         transform_key = SUPPORTED_TRANS.fetch(key, nil)
         transform_key ||= key
 
+        if transform_key == "oi" || transform_key == "di"
+          transformation[i][key][0] = "" if transformation[i][key][0] == "/"
+          transformation[i][key] = transformation[i][key].gsub("/", "@@")
+        end
+
+        transformation[i][key] = ERB::Util.url_encode(transformation[i][key]) if transform_key == "ot" || transform_key == "otf"
+
         if transformation[i][key] == "-"
           parsed_transform_step.push(transform_key)
         else