Clarify README section on differences with xz about pixz

[vasi]

Stdout is totally supported! I can do cat SOMEFILE | pixz | wc -c and I get totally reasonable results. Is there some situation where stdout is not working for you?

[bearrito]

@vasi Maybe I'm misinterpreting this statement, my fault if so.

pixz does not support the command line option -c or --stdout

Namely we have something like this

xz -d -c $IMAGE_PATH | sudo dd skip=$SKIP_BLOCKS of=$PARTITION 

[vasi]

Ah, so your problem is we don't have the exact same arguments as xz. But you can still do the same operation, just worded a bit different:

pixz -d < $IMAGE_PATH | sudo dd skip=$SKIP_BLOCKS of=$PARTITION

Probably we should edit the README.md to be clearer!

[bearrito]

Thanks for the fast response. Get some sleep (or not) !
I'll try that tomorrow!

[vasi]

Updated the readme!