Check for and use system proxies for downloading files
Check for and use system proxies for downloading files

In some cases when the user is using a proxy urlib.urlopen() will fail to successfully open https files. This prevents the retriever from accessing the scripts stored on GitHub and causes the installation to fail (see #268). This change checks for the existence of proxies and makes them available in a way that urllib.urlopen() can find them
goelakash/retriever,henrykironde/deletedret,embaldridge/retriever,goelakash/retriever,henrykironde/deletedret,davharris/retriever,davharris/retriever,davharris/retriever,embaldridge/retriever,embaldridge/retriever