Implement before_all and after_all

[mackwic]

As of today, we only have before_each and after_each. Implementing the after_all and before_all should be a piece of cake.

[JustinRyanH]

How up to date is this Issue? This looks like it has been finish in the documentation and the merge.

[regexident]

You are right. It was implemented in #30

[mackwic]

@JustinRyanH there is work to do on the formatters if you want to start with something no too hard but very useful. ;)

[regexident]

@JustinRyanH Also don't hesitate to ask questions. You will probably have a bunch.

This being said I think I should write a documentation on the internal structure once I find the time.
As in "what is happening when and how/why during a test suite execution?".