Introducing Events, Progress and a run command.

[veewee]

This PR will make it possible to:

• Hook in GrumPHP through events
• Display progress when runnning tasks. This way you know WHY a commit is taking a long time. It is always enabled at the moment but could be configurable in the future.
• A basic run command that will run the commands on all the files that are registered to git.
• A new locator that can find out which files are and will be committed to git.
• Use the grumphp command system-wide

This will resolve issues: #46, #33, #20 and #42.
For know it seems enough for CI to be able to run the tasks with the run command.

Another issue should be opened to make it possible to skip tests when running the tasks.

Can you take a look at this @aderuwe, @igormukhingmailcom ? Thanks!

[aderuwe]

There's an extra empty line here.

[aderuwe]

I'm 👍

[veewee]

I removed the newlines. However php-cs is not complaining and there are still other classes with extra newlines. Maybe the PHP-cs standard should be adjusted?