Are you cloning it into the Standards directory? See: https://github.com/x-team/wp-plugin-dev-lib/blob/d0194bb5fa9698a327fa67b373262a8ca83840fd/.travis.yml#L23

```
 git clone git://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards.git $(pear config-get php_dir)/PHP/CodeSniffer/Standards/WordPress)
```