Detect circular references and throw a LogicException (replaces #73)

With Pimple, it's easy to create services with a circular reference. This PR replaces #73 with the ability to throw an exception for any type of "factory" (shared service or not) and display the service name in the exception. 

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

This code is inspired by Symfony DI: 
https://github.com/symfony/symfony/blob/master/src/Symfony/Component/DependencyInjection/ContainerBuilder.php#L475