Move Provider logic in a compilerpass

[jderusse]

This PR allow users to define their own Providers.
Fixes #66

Sample of use

swarrot:
    provider: redis

services:
    app.swarrot.provider_factory:
        class: AppBundle\Provider\RedisFactory
        tags:
            - {name: swarrot.provider_factory, alias: redis}

[odolbeau]

Thanks for this contribution, it definitively sounds like a very good idea. :)

Can you correct tests please?

[jderusse]

Done.

Thanks @Taluu for the initial PR ;)

[stof]

this is broken in case the class is defined with a parameter. You need to resolve the value first

[jderusse]

good catch !