Use Proxy settings, able to ignore emailing

Hi, I slightly changed the script and the config file.
* Config File now has a section [proxy] with an option http_proxy
* Script reads in http_proxy from config (if defined) and passes it to the keyword argument of Shotgun class' __init__
* emails is not simply set to True, but extended the signature of Plugin's __init__ to contain a defaulted keyword arg and pass it through.
* getSMTPServer method now checks if the section has options (so that you don't need to set-up e-mail to test out the script

Some other minor changes made, hope this makes sense to you guys as well.