#46 - applying correct `chmod()` to generated cache file

See #46 ( https://github.com/doctrine/annotations/pull/46#issuecomment-67565499 ) 
In this way the `chmod` is done after the rename, making the operation not atomic. Consider moving it to before the `rename` block.

```
chmod($tempfile, 0666 & ~umask());
if (false === rename($tempfile, $path)) {
    throw new \RuntimeException(sprintf('Unable to rename %s to %s', $tempfile, $path));
}
```

Not sure why the @ would be needed, so removed it.