<issue_start><issue_comment>Title: Add superpixels support
username_0: in imgaug documentation they say, that they use skimage "slic" for function, but i can't reproduce result from imgaug function
maybe something is missed

there is things that arise with rewriting:
1. should we call new functions from imgaug-dependent ones(with "deprecated" warning) or should we completely destroy imgaug-dependent augs?
2. should we completely reproduce augmentation results of imgaug or, if this will be working faster and better, should we enhance options of usage(for example: "slic" function of skimage contains about 10 parameters, we can use them)

here picture with result for now
https://cdn1.savepice.ru/uploads/2020/12/14/eb600411f0e73d6531167d9b490483e7-full.png

passed tests and black formatting locally
<issue_comment>username_1: I'd say it's better to keep original names in the code & imports (But not in docs, he-he) and raise a warning:

```python
class Sharpen(A.ImageOnlyTransform):
   def __init__(...):
    ....
   ....

class IAASharpen(Sharpen):
   def __init__(...):
      warnings.warn("This augmentation is deprecated. Please use A.Sharpen instead").
```


Regarding second question - whenever possible we should keep the default behavior so the sake of backward compatibility. But exposing more parameters for more granular control of the augmentation is also highly appreciated!
<issue_comment>username_2: Thank you for your help.
What version of imgaug your implementation based on?
It looks like in latest imgaug this transform works a little bit different.
<issue_comment>username_0: Yes, in my enviroment it works also different
I'm trying to figure out why

All remarks have been notified, thanks!
<issue_comment>username_2: Implemented #849