SortedArray handles incomparable values poorly

[kriskowal]

If multiple, incomparable values are added to a sorted array, and subsequently removed, the sorted array should behave effectively like a plain array with push and pop. As yet, the search functions are returning indeterminate values and adding removing values from seemingly random positions.

See: montagejs/frb#13

[simon-weber]

One problem I see is that callers of search that deal in equality (eg searchFirst/Last) make assumptions about the equality of elements around the result index. But, search only guarantees that the index is somewhere in streak of one or more incomparable values.

I think the fix is to adjust searchFirst/Last to scan both left and right from search's index, then scan within that range for their final result.