Resolve issues with Symfony dependencies

[djmattyg007]

This commit removes the dependency on the Symfony Config component. The
only code other than getters that was actually being used was the
constructors. In symfony 2, these were incredibly basic. In symfony 3,
they perform some validation.

This validation was causing a couple of "does not exist" tests to fail,
as the Symfony Config module was performing these checks before the
Lurker module, and throwing a different exception. Removing this
dependency neatly solves this issue at the same time.

[djmattyg007]

Please note that until #24 is merged as well, the tests will continue to fail despite these improvements.

[totten]

Belated cheers @djmattyg007. I combined this with another/similar patch to remove symfony/event-dispatcher -- published as lurkerlite. This should be less picky about dependencies.

[djmattyg007]

You should merge #24 too, as that should fix the issues you saw with inotify tests. Do you think you'd be able to open the issue tracker on your repo?