Side note, on Windows 10, uploading fails because ftd2xx.dll is missing and ujprog.exe won't run without it. I was able to fix this by downloading the FTDI driver from http://www.ftdichip.com/Drivers/D2XX.htm and putting the DLL in C:\Users\AppData\Local\Arduino15\packages\FPGArduino\tools\ujprog\1.0.0. I had to find ujprog.exe and run it manually to see the error dialog about the missing DLL. The Arduino IDE did not display any errors to indicate that this was the problem so this should probably be documented.
From J.B. Langston
Side note, on Windows 10, uploading fails because ftd2xx.dll is missing and ujprog.exe won't run without it. I was able to fix this by downloading the FTDI driver from http://www.ftdichip.com/Drivers/D2XX.htm and putting the DLL in C:\Users\AppData\Local\Arduino15\packages\FPGArduino\tools\ujprog\1.0.0. I had to find ujprog.exe and run it manually to see the error dialog about the missing DLL. The Arduino IDE did not display any errors to indicate that this was the problem so this should probably be documented.