* fixed `CompositeModel` and added it to docs
* added `L0` and `Linfinity` (`Linf`) distance measures
* added `DeepFoolLinfinityAttack`
* renamed `DeepFoolAttack` to `DeepFoolL2Attack`
* new `DeepFoolAttack` now chooses norm to optimize based on the employed distance measure (alternative, `p=2` or `p=np.inf` can be passed)
* fixed integer overflows caused by numpy
* improved tests