Added proxy support for web api

My corporate datacenter deployment requires proxying for external requests. Current workaround requires installing a global opener in urllib2 (and uninstalling after request completion). 

This is a better solution which allows specifying a proxy address for web api requests.

Here is a silly image that shows a proxy setup, found on Google Images: 

![](http://www.xda-developers.com/wp-content/uploads/2013/08/about-proxy-server.jpg)