fix for #145 - add vmimage support, honor http 307 redirects 

Changed virtual machine management and image management to use vmimages in addition to os images.  Also added redirect code for http 307 response codes.  I made these changes because we are no longer able to use the azure gem (or vagrant azure) to create new VMs from custom images that we create.  I believe there may have been a change this month where user vmimages that are captured are treated differently than standard OS images.  This code seems to work, but it took a lot of trial and error as I couldn't find very good documentation.  I'm happy to do some further refining of this code if I were pointed to the documentation detailing the differences between /services/images and /services/vmimages, as well as the proper deployment options.