Add a test case for the dumped Symfony2 Router.

I've added an additional test case for Symfony2 where the routes are dumped, like it should be done in a production environment.

Interestingly, with this change the Symfony2 Router is the fastest on my machine. I'll be interested in the results with the Pux extension.

I didn't update the Readme.md, I'll leave that to you. For reference here are my results (5.4.17).

Unknown route

Test Name | Time | +Interval | Change
--------- | ---- | ---------- | ------
Symfony2 Dumped  | 0.0000399455 | +0.0000000000 | baseline
FastRoute | 0.0002344939 | +0.0001945484 | 487% slower
Symfony2  | 0.0010168788 | +0.0009769332 | 2446% slower
Pux PHP | 0.0012545040 | +0.0012145585 | 3041% slower

Last route

Test Name | Time | + Interval | Change
--------- | ---- | ---------- | ------
Symfony2 Dumped | 0.0001198003 | +0.0000000000 | baseline
FastRoute  | 0.0002490872 | +0.0001292869 | 108% slower
Symfony2  | 0.0011074704 | +0.0009876701 | 824% slower
Pux PHP | 0.0014067766 | +0.0012869763 | 1074% slower

First route

Test Name | Time | + Interval | Change
--------- | ---- | ---------- | ------
FastRoute | 0.0000158739 | +0.0000000000 | baseline
Pux PHP | 0.0000176847 | +0.0000018108 | 11% slower
Symfony2 Dumped | 0.0000331372 | +0.0000172633 | 109% slower
Symfony2  | 0.0001584002 | +0.0001425263 | 898% slower