Re-implement a solution for the first day 1 puzzle, move common code into a library package.

2018/day01-1.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"internal/calibration"
+)
+
+// Provide a filename as input, get the result on stdout
+func main() {
+	x := 0
+	seen := calibration.Set{} // we don't use this until day01-2, just added here for backwards compatibility
+
+	x, _ = calibration.ScanFrequencies(os.Args[1], &seen, x)
+
+	fmt.Println("Frequency list scanned, calibration complete: ", x)
+}