mkdir() latest version of Hummingbird

Hi there,

The latest version of hummingbird appears to try to make a logging directory.

Since my site is on a host (Pantheon) where the file system, outside of the WP uploads folder, is locked down, this fails and I get the following warning.

Warning: mkdir(): Permission denied in /srv/bindings/391c23d8a01649b98aef6fd482ce72f1/code/wp-content/plugins/wp-hummingbird/core/class-logger.php on line 132

I understand this is just a warning, and warnings are already hidden on my production environment. However, I don't want to disable warnings on my dev and test environments.

It would be great if this log could be created in a similar location to where minified code it placed, of if it can be disabled.