Router.start() called more than once

[wallzero]

With @uirouter/react@1.0.1, I receive the following error with <React.StrictMode>:

core.js:71 Uncaught Error: 
  The Router.start() method has been called more than once.

  The <UIRouter> component calls start() as final step of the initialization and you shouldn't need to call it manually.

[christopherthielen]

fixed by #607