Make -t mandatory

[LukeSavefrogs]

Problem

Right now the behaviour is not quite clear for people used to column, since the -t parameter can be omitted.

Enforcing using it may help in understanding that ONLY the "table mode" is supported

Solution

The program should exit with error if the -t parameter is not supplied, to make it clear that ONLY the "table" mode is supported.

• Before:

$ printf "1 2 3" | column_ansi
1  2  3

• After:

$ printf "1 2 3" | column_ansi
Error: column_ansi only supports the "table" mode from the original `column` command

Also, the inline help should refleact this change:

• Before:

$ column_ansi.sh --help
USAGE:
        column_ansi [-s SEPARATOR] [-o SEPARATOR] [-R COLUMNS] [-H COLUMNS] [-C COLUMNS]      
        column_ansi --help

OPTIONS:
        -t, --table
                Does nothing, was left for compatibility reasons. [DEFAULT]

• After:

$ column_ansi.sh --help
USAGE:
        column_ansi -t [-s SEPARATOR] [-o SEPARATOR] [-R COLUMNS] [-H COLUMNS] [-C COLUMNS]      
        column_ansi --help

OPTIONS:
        -t, --table
                Create a table, required to make this behaviour explicit.