Adding link to windows downloads

New windows builds with ITK_USE_64BITS_IDS enable. This add support
for 4-gigapixel images to the windows 64 builds.

Change-Id: I3046a9d839170156109d4714dc2f389ba6caccb0
Merge topic 'AddPythonDownloads0.7.1.post1-1'

b7f0237 Adding link to windows downloads