[NICETHING beta] assert `needs` incompatibility with periods

needs isn't compatible with periods, because ultimately
you're going to need to call get('controllers.foo.bar')
(assuming needs: 'foo.bar'), which doesn't and can't
do what you want.
[BUGFIX beta] New error stack trace

Related [#67](https://github.com/tildeio/router.js/pull/67).
Merge pull request #3876 from twokul/relevant-stack-trace

[BUGFIX Beta] New error stack trace
Merge pull request #3899 from machty/needs-warning

[NICETHING beta] assert `needs` incompatibility with periods