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.

test/unit/post_test.rb

@@ -17,14 +17,12 @@ class PostTest < ActiveSupport::TestCase
       @user = FactoryBot.create(:user)
     end
     CurrentUser.user = @user
-    CurrentUser.ip_addr = "127.0.0.1"
   end
 
   def teardown
     super
 
     CurrentUser.user = nil
-    CurrentUser.ip_addr = nil
   end
 
   context "Deletion:" do