microsoft: add windows live endpoints
microsoft: add windows live endpoints

Change-Id: I205dfb6c4d693929da799dcba40b3539c6302100
Reviewed-on: https://go-review.googlesource.com/18691
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/oauth2,drewwells/oauth2