Fix percentage reading

Don't skip every 2nd output line from raw_write.py, so that odd numbers of lines do not falsely cause an error.
Increase block size, check read length

Increased blocksize to reduce I/O overhead.  Disabled printing total_size to avoid an error in mintstick.py's progress bar.  Add the actual length of the buffer contents to "size" instead of the ideal blocksize.
Merge pull request #8 from cpuprocess/master

Block size will be set to something lower than 32768. 32768 just show the user it's finished, but it usually don't : data is still writed from the buffer.