rust/2016: remove all traces of year 2016

Since I have now solved year 2016 in Java, there is no need to have
any solution code here.

Author: saser

rust/src/lib.rs

@@ -1,7 +1,6 @@
 use std::io;
 
 pub mod base;
-pub mod year2016;
 pub mod year2017;
 pub mod year2018;
 

rust/src/main.rs

@@ -59,8 +59,6 @@ fn imain() -> i32 {
     };
     // Choose solution function based on arguments.
     let solution: Result<aoc::Solution, String> = match (year, day, part) {
-        // Year 2016.
-        (2016, 1, 1) => Ok(aoc::year2016::day01::part1),
         // Year 2017.
         (2017, 1, 1) => Ok(aoc::year2017::day01::part1),
         (2017, 1, 2) => Ok(aoc::year2017::day01::part2),