Remove Binary Search

* [ x] I've read, understood, and done my best to follow the [*CONTRIBUTING guidelines](https://github.com/jjatie/Charts/blob/master/CONTRIBUTING.md).

## Background
Binary search provides optimized search for sorted collections. For unsorted collections, binary search is significantly slower than iterating over the collection. Charts implements binary search, however it does not enforce sorted collections, causing significantly slower lookup times for unsorted collections.

## Proposal
Remove binary search until such a time that we can a) enforce sorted chart data or b) have sorted and unsorted chart data with different look up algorithms.

## Charts Environment

**Charts version: 3.2
**Xcode version:10
**Swift version:4.2