finish day 1, part 2

src/main.rs

@@ -1,5 +1,7 @@
 mod day_1;
 
 fn main() {
-    println!("{}", day_1::day_1());
+    let day_1_input = std::fs::read_to_string("input/day_1.txt").unwrap();
+    println!("Day 1, part 1: {}",   day_1::part_1(&day_1_input));
+    println!("Day 1, part 2: {:?}", day_1::part_2(&day_1_input));
 }