- moved getLongest function into getSubSeries as nested function because it does not serve as a generic Array.prototype function when it gets the longest and highest sum in case of ties
- removed Array.prototype.getLongest
- moved Array.prototype.equals back into tests.js since it is only used in test code
- combined getLongest and check for sums into a single function to save looping over the subseries collection twice
- added a test over a large array (100 elements) as a performance test