removed superfluous Foo and test standing in the way

this testcase is standing in the way when using composer for dependency
management.

also it is most likely not needed any longer as slim uses per its
composer file the psr-0 autoloader from composer.

i therefore came to the assumption that this is just old, dead code.

removed the test and the not anywhere else used Foo class.

this is also in preparation for further commits.
switched to composer autoloader

after c40666b autoloading can be fully delegated to composer and the
bootstrap file for testing can be replaced by it.
squash? Modified Slim/Log to be more PSR-3 Compliant

This implements Psr\Log\LoggerInterface to actually make the logger
PSR-3 compliant.

This is a separate commit that *could* be squashed into the previous
ones after ae7baed and c40666b are incorporated - which they could
independently.