IRR improvement: use [binary search] idea to improve both performance and [result value range].

[jxjjligang]

The current IRR function has 2 problems that I noticed.

1. It uses linear increment/decrement iteration to approach the result, which is both time consuming and can't guarantee a result returned.
2. The boundary of the result rate is not clear to external user.

My code change will fix above problems.

1. Binary search will greatly reduce CPU time and guarantee get a result.
2. The boundary of the result rate is [-99.999%, 10000%], will be enough for most real world scenarios.

[jxjjligang]

I have also run "npm test", which passed all the cases.
The IRR function result is exactly the same after my change.