[WiP] RSpec improvements and upgrade to RSpec 3.0

This is a working progress PR, initially started with the motivation in mind to provide clarity to the LogStash tests and to upgrade them to 3.0

This is an WiP PR, that is mainly open so we can reach a common point on how do we want to have our test looking like. 

If you have any question or doubt about why something is like it is, fire a comment :smile: 

- purbon
Actually is not the setup, but somehow I agree with you that the knowledge you could grasp having the hole configuration in the test is now hidden under the fixtures.

My thing here is somehow I want to simplify this kind of data, so we don't have big chunks of text in the middle of our tests .... so we have simple tests explanations. I think to make that happen, we can use fixtures or factories (mostly used for object, not for configuration texts), both of them have supporters and detractors, ....  any ideas is highly welcome