cosmiconfig(...).search() is not a function

I've run into an error, but I'm not sure what has triggered it. Here is the error message:

```
DONE Compiled successfully in 1121ms
...\build\index.js:103
const explorer = cosmiconfig('graphpack').search();
^

TypeError: cosmiconfig(...).search is not a function
at Object../node_modules/graphpack/config/index.js (...\build\index.js:103:43)
at __webpack_require__ (...\build\index.js:21:30)
at Module../node_modules/graphpack/lib/server.js (...\build\index.js:240:65)
at __webpack_require__ (...\build\index.js:21:30)
at Object.0 (...\build\index.js:700:18)
at __webpack_require__ (...\build\index.js:21:30)
at ...\build\index.js:85:18
at Object. (...\build\index.js:88:10)
at Module._compile (module.js:652:30)
at Object.Module._extensions..js (module.js:663:10)
```

I've tried running `graphpack` and `graphpack build` then `node ./build/index.js`, but both methods throw this error.