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

	len = ceil( ( x2-x1 ) / increment );
	if ( len <= 1 ) {
		return [ x1 ];
	}
	arr = [ x1 ];
	for ( i = 1; i < len; i++ ) {
		arr.push( x1 + (increment*i) );
	}
	return arr;
}
Generates a linearly spaced numeric array according to a provided increment.

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

@example
var arr = incrspace( 0, 11, 2 );
// returns [ 0, 2, 4, 6, 8, 10 ]