Easy to setup gem

I added some features to enable a more simple and easy setup:

* An easy to setup gem, throw the possibility to have uncommon/standard path names for configurations and inputs (throw a config file)
* Added some more resilience throw more test in rspec.
* Added some generalisation throw dependency injection.
It will be clearer on the required format if we use `.lsit.yml` for the filename.
And what `lsit` mean? it is `Logstash integration test` ?