* added the `options` field to dagre's `setEdge`
* added a test as well
* changed some style issues according to linter (var -> let)
* exported `dagre-d3` so it is possible to import it with SystemJS
* Atom's TypeScript package now accepts the import
* changed some style issues according to linter (var -> let)
* changed `let` to `const` whenever it is possible.
* changed `let` to `const` whenever it is possible.
* `const` is possible here as well because the object reference does not change.