Convert batch parameters to uppercase

**listBatchSubscribe** throws an 'Invalid Email Address' error when using the lowercase 'email' batch parameter. [Documentation for v1.3 API](http://apidocs.mailchimp.com/api/1.3/listbatchsubscribe.func.php) suggests using the uppercase key name 'EMAIL' . 
For consistency, I've updated the other 4 parameters, although it isn't necessary.