Add "yyyy-MM-dd HH:mm:ss" string format

diff --git a/cast_test.go b/cast_test.go
index 6b73ff8..2e418ec 100644
--- a/cast_test.go
+++ b/cast_test.go
@@ -212,3 +212,10 @@
 		assert.Equal(t, v.expected, ToDuration(v.input))
 	}
 }
+
+func TestStringToDate(t *testing.T) {
+	d := "2016-03-06 15:28:01"
+	format := "2006-01-02 15:04:05"
+	v, _ := time.Parse(format, d)
+	assert.Equal(t, ToTime(d), v)
+}
diff --git a/caste.go b/caste.go
index 23f59a1..23f0fe8 100644
--- a/caste.go
+++ b/caste.go
@@ -513,6 +513,7 @@
 		"02 Jan 2006",
 		"2006-01-02 15:04:05 -07:00",
 		"2006-01-02 15:04:05 -0700",
+		"2006-01-02 15:04:05",
 	})
 }