Integer problem starting with 0

## Feature
```python
0123
```

Integer starting with 0 should raise SyntaxError.
I think it should be fixed in lexer.rs

### Expected Result
```python
>>> 0123
  File "<stdin>", line 1
    0123
       ^
SyntaxError: invalid token
```
### Actual Result
```python
>>>>> 0123
123
```
