FileIO.cpp fix on File::doBuffer()

[dreggy]

Using the Bridge library for the Arduino Yùn I noticed a losses of bytes while reading files from the Yùn. This happens only when the file is larger of the buffer on FileIO.h

Actually i fixed this changing in the file FileIO.cpp the line 121:
uint8_t cmd[] = {'G', handle, sizeof(buffer)};
to:
uint8_t cmd[] = {'G', handle, sizeof(buffer)-1};

maybe the bug is caused by the shift routine at line 127~128

[cmaglie]

@dreggy

yeah, there is a buffer overflow in this function, and your solution fix it correctly.
I'm going to commit it for the next release.

Thank you!
C