Fix format option and add bootstrap option.

[Moult]

Addresses issue #52.

It seems to work, but unsure if it is structured well.

[everzet]

1. There still should be way to provide default formatter through phpspec.yml when no option in CLI is provided.
2. Bootstrap file is just a file that you need to require - it's not Runner responsibility. It could be simply done in Application
3. Application-level options should be handled little-bit different (not in commands). Look for:
   • https://github.com/symfony/Console/blob/master/Application.php#L918-931
   • https://github.com/symfony/Console/blob/master/Application.php#L146-150

[henrikbjorn]

Seems wierd you are going to give it a path without the extension?