added shift function and tests

cpu/operations/shift.go

@@ -0,0 +1,5 @@
+package operations
+
+func Shift(r1 *byte) {
+	*r1 = *r1 << 1
+}

cpu/operations/shift_test.go

@@ -0,0 +1,17 @@
+package operations
+
+import (
+	"testing"
+)
+
+func TestShift(t *testing.T) {
+	r1 := byte(0b01010101)
+	Shift(&r1)
+
+	expected := byte(0b10101010)
+	actual := r1
+
+	if actual != expected {
+		t.Errorf("actual %x != expected %x", actual, expected)
+	}
+}