change delta T formula and add planet phenomena function

mercury/mercury_test.go

@@ -0,0 +1,14 @@
+package mercury
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestMercury(t *testing.T) {
+	date := time.Now().Add(time.Hour * -24)
+	fmt.Println(CulminationTime(date, 115))
+	fmt.Println(RiseTime(date, 115, 23, 0, false))
+	fmt.Println(DownTime(date, 115, 23, 0, false))
+}