Print results as as 4 columns by default, seperated with tabs.

Output of the read-meter command can then be piped to other scripts
and read like this (e.g. generate a SQL insert statement):

    IFS='{tab}'
    while read date kwh1 kwh2 gas; do
      echo "INSERT INTO data VALUES ('$date', $kwh1, $kwh2, $gas);"
    done < /dev/stdin