Make it possible to set your path for the workingDir variable

[iandreyev]

If running on a Linux system where systemd has PrivateTmp=true (which is the default on CentOS 7 and perhaps other newer distros), this function will simply return "/tmp", not the true, much longer, somewhat dynamic path.

I have PHP Fatal error: Uncaught exception 'Exception' with message 'Error in initializing working copy of the template'

[Raaghu]

@iandreyev Please open a pull request with you changes.