Support specifying trailing indents for div columns

[roryokane]

Support for this would be required to implement yargs/yargs#1640.

The idea is to add support for trailing indents to the div function.

One possible API would be supporting an option multilineIndents for each column passed to div. That option would take an array of two numbers [leadingIndent, trailingIndent] with these meanings:

• leadingIndent (number): how many spaces to add to the start of the first line in that column
• trailingIndent (number): how many spaces to add to the start of each line after the first