I have created a new project in Xcode 6.0.1 and created the following Podfile:
source \'https://github.com/CocoaPods/Specs\' platform :ios, \'8.0\' pod \'AF
Just delete all configs in the the Pods Group in xcode and run pod install again. This will regenerate the xcconfigs files. Then make sure they are set properly in the Project > Info > Configurations