PSeries = function(list, repeats, offset) {
    Pattern.call(this);
    this.list = list;
    this.repeats = repeats || 1;
    this.position = 0;
    this.offset = offset || 0;
}
Iterate through a list of values.

@constructor
@extends Pattern
@param {Object[]} list Array of values.
@param {Number} [repeats=1] Number of values to generate.
@param {Number} [offset=0] Index to start from.