Leading spaces with echo + keepWords

[jcubic]

Issue summary

When you echo text with longer spaces it means have leading spaces

Expected behavior

Leading spaces should be removed

Actual behavior

There are leading spaces

Steps to reproduce

1. Open https://codepen.io/jcubic/pen/oNoaGyv?editors=0010
2. Or use code:

var lines = $.terminal.split_equal('This   is    some    text   with   spaces', 20, true);
term.echo(lines.join('\n'));

This bug is introduced by #738