Vector encoder

adds ability to `MultiEncoder` to encode(dict) (default, now) + new: `encode([list])`, encode([numpy.ndarray]) 
transparently with overloading. Can do even encode([1, "cat", "fat", 45]) 
Can ouptut in any of those formats as well. 

It's for convenience mostly, wrapping and little bit enhancing the current MultiEncoder. 

New class SimpleVector with easy constructor which is an array of integers encoded by scalar encoders. 
I find array/list as heavily useful for daily use. 

This is ready for merging. 

Please note a "bug" in encoding [1, "str"] as numpy.ndarray, all elements are converted to strings!, so either use one of `dict/list` and `ndarray` just for numbers.

Thanks for reviewing!