Add support for Express 4.x

Since Express 4.x removed Connect from it's core, but using the same routing functionality, they have moved `app.stack` to `app._router.stack`. With this pull request, I've implemented a check for both along with error handling if neither are found. I also bumped the version to `0.0.6` along with updating `History.md` with the changelog.

Let me know if you have any questions on this change.