README.md in cupertino-0.6.1

- old
+ new

@@ -17,10 +17,10 @@
 
 ```sh
 $ ios login
 ```
 
-_Credentials are saved in the keychain. You will not be prompted for your username or password by commands  while you are logged in._
+_Credentials are saved in the Keychain. You will not be prompted for your username or password by commands while you are logged in. (Mac only)_
 
 ### Devices
 
 ```sh
 $ ios devices:list