function lpad( str, len, pad ) {
	var n = ( len - str.length ) / pad.length;
	if ( n <= 0 ) {
		return str;
	}
	n = ceil( n );
	return repeat( pad, n ) + str;
}
Left pads a string such that the padded string has a length of at least `len`.

@param {string} str - string to pad
@param {NonNegativeInteger} len - minimum string length
@param {string} pad - string used to pad
@returns {string} padded string

@example
var str = lpad( 'a', 5, ' ' );
// returns '    a'

@example
var str = lpad( 'beep', 10, 'b' );
// returns 'bbbbbbbeep'

@example
var str = lpad( 'boop', 12, 'beep' );
// returns 'beepbeepboop'