If your babelrc file is not in cwd but in the file path, it is not used in the cache key

e.g.

```
/ src
/ src / file.js
/ src / .babelrc
/ test
/ test / test.js
/ test / .babelrc
```

then the babel rc is resolved to undefined. Changing the babelrc file does not update the cache.

PR will be raised shortly..
