Please move `@types/zen-observable` from devDependencies to dependencies about apollo-link

[jbaxleyiii]

@foisonocean @Grmiade or anyone else want to open a PR for this? It be a great first contribution!

[Grmiade]

Any news?

[Grmiade]

This issue is fixed for me. Indeed,@types/zen-observable seems be a dependencies.
https://github.com/apollographql/apollo-link/blob/master/packages/apollo-link/package.json#L44

[evans]

Thank you @alvis for #171!

[plinionaves]

Did not work for me... :(

I had to go in my node_modules/@types/zen-observable/index.d.ts and add this to the end of the file:

export default Observable;

Why?

Note: I replaced this:
export = Observable
By the line mecioned above