function unitspace( x1, x2 ) {
	var arr;
	var len;
	var i;

	len = x2 - x1;
	if ( len <= 1 ) {
		return [ x1 ];
	}
	arr = [ x1 ];
	for ( i = 1; i < len; i++ ) {
		arr.push( x1 + i );
	}
	return arr;
}
Generates a linearly spaced numeric array whose elements increment by 1.

@param {number} x1 - first array value
@param {number} x2 - array element bound
@returns {Array} linearly spaced numeric array

@example
var arr = unitspace( 0, 6 );
// returns [ 0, 1, 2, 3, 4, 5 ]