Remove date regexp (#447)

* Remove date regexp

Hand-roll the date matching logic to avoid trying to match a regexp on
every integer.

```
benchmark                    old ns/op     new ns/op     delta
BenchmarkUnmarshalToml-8     293449        272134        -7.26%

benchmark                    old allocs     new allocs     delta
BenchmarkUnmarshalToml-8     2746           2650           -3.50%

benchmark                    old bytes     new bytes     delta
BenchmarkUnmarshalToml-8     133604        127548        -4.53%
```

* Remove fuzzit

The company has been acquired by GitLab and shutting down.

token_test.go

@@ -25,8 +25,9 @@ func TestTokenStringer(t *testing.T) {
 		{tokenRightParen, ")"},
 		{tokenDoubleLeftBracket, "]]"},
 		{tokenDoubleRightBracket, "[["},
-		{tokenDate, "LocalDate"},
 		{tokenLocalDate, "LocalDate"},
+		{tokenLocalTime, "LocalTime"},
+		{tokenTimeOffset, "TimeOffset"},
 		{tokenKeyGroup, "KeyGroup"},
 		{tokenKeyGroupArray, "KeyGroupArray"},
 		{tokenComma, ","},