Complaints about react dependencies

[tmickel]

On a fresh clone and npm install:

npm WARN EPEERINVALID scratch-gui@0.1.0 requires a peer of react@15.x.x but none was installed.
npm WARN EPEERINVALID scratch-gui@0.1.0 requires a peer of react-dom@15.x.x but none was installed.

[tmickel]

Fixed these with a manual install of both, but I'm guessing that shouldn't be necessary.

[rschamp]

Fixed in edd09fa