Adds data collector

[nunomaduro]

The Symfony Profiler obtains its profiling and debug information using some special classes called data collectors.

It may be a good idea restore this feature from: #57.

[kiler129]

I can take a peek at this if you want. Do you expect just restoring the same functionality or improving it in some way? ;)

[nunomaduro]

@kiler129 Thank you! We are open for sugestions, but would be cool to have this.

[ostrolucky]

This feature was unfortunately never merged upwards. Why? It is in 2.x.