Fix for PHP 5.3.7

In PHP 5.3.7 the following errors occurs:

[2013-10-18 11:31:45] log.ERROR: exception
'Symfony\Component\Debug\Exception\FatalErrorException' with message
'Using $this when not in object context' in
/home/azie01/domains/azie.justnotfinished.com/laravel/vendor/hugofirth/m
ailchimp/src/Hugofirth/Mailchimp/MailchimpServiceProvider.php:34
Stack trace:
#0 [internal function]: Illuminate\Exception\Handler->handleShutdown()
#1 {main} [] []