Search For A Range

Given a sorted array of integers, find the starting and ending position
of a given target value.

		Your algorithm's runtime complexity must be in the order of O(log n).

		If the target is not found in the array, return [-1, -1].

		For example,
		Given [5, 7, 7, 8, 8, 10] and target value 8,
		return [3, 4].