FIX: hook slim.after is called before response was sent

Signed-off-by: Max-Julian Pogner <max-julian@qyanu.com>
Merge pull request #703 from qyanu/release-2.4.1

FIX: hook slim.after is called before response was sent
Detect circular middleware stacks and throw comprehensible exception.
Merge pull request #715 from marcioAlmada/release-2.4.1

release-2.4.1 Detect circular middleware stacks
Merge lost branch 'release-2.4.1' into release-2.4.3
Merge pull request #785 from qyanu/release-2.4.3

branch release-2.4.1 dropped without merging fixes?