Filling in Accumulator implementation and test client

as well as fixing the Canvas implementation so that it doesn't pop up an
X window on init.

algs4/src/go/algs4-test-accumulator/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+
+	"github.com/meatballhat/box-o-sand/algs4/src/go/algs4"
+)
+
+func die(err error) {
+	fmt.Fprintf(os.Stderr, "ERROR: %v\n", err)
+	os.Exit(1)
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		die(errors.New("We need an int!"))
+	}
+
+	nValues, err := strconv.Atoi(os.Args[1])
+	if err != nil {
+		die(err)
+	}
+
+	a := algs4.NewAccumulator()
+	for t := 0; t < nValues; t++ {
+		a.AddDataValue(algs4.Random())
+	}
+
+	fmt.Println(a)
+	return
+}