Print messages to stderr when output is piped

[0WN463]

Depends on #339

When qrcp sees that the output is piped, it will now print its messages to stderr instead of stdout, to allow easy piping of output.

# saves file with the file path of ./piped_file
./qrcp receive  --file - > piped_file

# sends received data to clipboard manager
./qrcp receive  --file - | $CLIPBOARD_MANAGER