Add license information

Its great the project is MIT licensed as per the [package.json](https://github.com/the-grid/the-graph/blob/master/package.json#L31) and the [parent project notices](https://github.com/noflo/noflo-ui/blob/master/LICENSE-MIT).

However the license information is not as prominently displayed as it could be, which makes it harder for people to find.