Increase portdelay so the Arduino Uno R3 works.

The Arduino Uno R3 requires a longer device.open.portdelay compared to
older Arduino boards.
This fixes the reported issue of device timeouts.  Tested on Mac OSX
and Windows and the R3 works fine with this delay.  Also tested against
original Uno, Duemilenove, Seeeduino and they still work.
Merge pull request #186 from gillham/master

Increase portdelay so the Arduino Uno R3 works.