Getting the Adafruit serial cable to work on OS X 10.10 (Yosemite)

After trying for a couple of hours to get the Adafruit serial cable to connect to my Raspberry PI A+ I learned some lessons:

1. You can power the Raspberry using the USB cable alone. If you connect your A+/B+ to a power source do not connect the red lead to the Raspberry PI. 
2. Always read the instructions before connecting your computer to anything (DUH :-).
3. Apart from how to connect the cable to the Raspberry PI the Adafruit guide:
        https://learn.adafruit.com/adafruits-raspberry-pi-lesson-5-using-a-console-cable/overview
   ...is somewhat out of date.
4. The OS X driver linked to from the Adafruit article:
         http://changux.co/osx-installer-to-pl2303-serial-usb-on-osx-lio/
   ...has issues with Yosemite, all you get when you install it and run the screen command is a blank terminal window. If you check in the console logs you will find something resembling the following entries.
   
   28/09/15 22:28:36,000 kernel[0]: nl_bjaelectronics_driver_PL2303(0xffffff8029049800)::allocateResources failed - no fpInterface.
   28/09/15 22:28:36,000 kernel[0]: nl_bjaelectronics_driver_PL2303(0xffffff8029049800)::start Allocate resources failed
   28/09/15 22:28:36,000 kernel[0]: nl_bjaelectronics_driver_PL2303(0xffffff8029049800)::CheckSerialState - StartSerial failed
   
   ...the reason for this is apparently that the driver has issues with OS X kernel signing.
5. After growing sick and tired of trying to get this thing to work I uninstalled it:
   
   sudo rm -r /System/Library/Extensions/osx-pl2303.kext
   sudo kextunload /System/Library/Extensions/osx-pl2303.kext
   
   and found out that there is a manufacturer supplied driver for the PL2303:
         http://www.prolific.com.tw/us/showproduct.aspx?p_id=229&pcid=41
   ...that now supports OS X10.10 and OS X 10.11 (El Capitan). After installing it the Adafruit Serial/USB cable finally worked. Don't be fooled if you get a blank terminal window after running the screen command:
   
         screen /dev/cu.usbserial 115200
   
   ... for some reason the 'raspberrypi login:' prompt did not appear on my system but entering the username and hitting [Return] caused the  familiar 'Password:' prompt to appear.
6. Finally, if you get a bunch of errors like this:
   
         Cannot open line '/dev/cu.PL2303-000013FA' for R/W: Resource busy
   
   ...or:
   
        dev/cu.PL2303-000013FA: ioctl TIOCEXCL failed: Resource busy
   
   It may be because you are improperly terminating the screen command. The proper way is:
   
         [Ctrl]+[A], then [K] and finally, [Y] to shut the program down.