Write a function longest_run that takes as input an array of 0's and 1's and outputs the length and index of the longest consecutive run of either 0's or 1's. If there are multiple runs of the same length, it should output the first occurence.

Examples:

1. longest_run([1 1 0 1]) should output [2 1], since the longest consecutive run is 11, which starts at index 1

2. longest_run([1 1 0 1 0 0 0 0 1 1 1]) should ouptut [4 5], since the longest consecutive run is 0000, which starts at index 5

3. longest_run([1 0]) should ouptut [1 1], since the first longest consecutive run is 1, which starts at index 1