Remove CurrentUser.ip_addr.

Remove the `CurrentUser.ip_addr` global variable and replace it with
`request.remote_ip`. Before we had to track the current user's IP in a
global variable so that when we edited a post for example, we could pass
down the user's IP to the model and save it in the post_versions table.
Now that we now longer save IPs in version tables, we don't need a global
variable to get access to the current user's IP outside of controllers.

app/controllers/dmails_controller.rb

@@ -38,7 +38,7 @@ class DmailsController < ApplicationController
   end
 
   def create
-    @dmail = authorize(Dmail).create_split(from: CurrentUser.user, creator_ip_addr: CurrentUser.ip_addr, **permitted_attributes(Dmail))
+    @dmail = authorize(Dmail).create_split(from: CurrentUser.user, creator_ip_addr: request.remote_ip, **permitted_attributes(Dmail))
     respond_with(@dmail)
   end