Fixing curl upload for PHP 5.6+

[caiovlp]

Curl safe upload is preventing laraworker to upload code to the server.

Here's where I reported the issue originally:
iron-io/laraworker#5

Setting CURLOPT_SAFE_UPLOAD resolved the issue.

[thousandsofthem]

Thanks, looks good!
Is it safe to set this option on older php installations? (Like 5.3)

[giorgiosironi]

This constant has been introduced in 5.5 so it's not safe to set it for previous versions.