How to find wifi passwords in Yosemite or iOS8
Keychain Access still stores the passwords: 

Go to Applications > Utilities and open the Keychain Access app. On the left side field, click "System," and in the left field "Category" click "Passwords". From here, you can double-click on each network in the "Name" column, and click the "Show password" box to show the network password. You may have to enter your Mac's Username/Password to view each Network Password.

I'm not aware of any way to do this direct from iOS 8, but your iOS passwords will be stored here as well. If you don't see them, on your iOS device, go to Settings > iCloud > Keychain, and turn on "iCloud Keychain" if it isn't already. Apple may text you a security code to verify this: Enter the code on your iOS device. Your saved Wi-Fi passwords should show up shortly, but you may have to close and re-open Keychain Access.