[BUGFIX][QueryParams] - Support for empty string QPs

This PR actually only adds tests to verify a fix
made in the route-recognizer. It should fix this bug:
https://github.com/emberjs/ember.js/issues/4054

This PR depends on: https://github.com/tildeio/route-recognizer/pull/19

That above PR changes the how QPs are parsed so that

`route/?foo` => `{ foo: true }`
and
`route/?foo=` => `{foo: ''}`