Fix #29
Fix #29

Instead of relying on tell() (which several sorts of streams aren't
going to support), it's better to simply accept and ignore the None
return value for the write() method as Python 2's mechanism for
reporting unsuccessful writes (whole or partial) is simply to raise an
exception instead of returning anything.

waveform80/picamera,tfroehlich82/picamera,rocky1001/picamera,ListFranz/picamera