Warnings during yarn add

Two specific warnings show up during `yarn add <package>`
```
warning fsevents@1.1.1: The platform "linux" is incompatible with this module.
warning "express-graphql@0.6.4" has incorrect peer dependency "graphql@^0.5.0-b || ^0.6.0 || ^0.7.0 || ^0.8.0-b || ^0.9.0".
```