Add TransitionChoice with repetitions

[jrapin]

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Motivation and Context / Related issue

How Has This Been Tested (if it applies)

Checklist

• The documentation is up-to-date with the changes I made.
• I have read the CONTRIBUTING document and completed the CLA (see CLA).
• All tests passed, and additional code has been covered with new tests.

[teytaud]

Thank you so much!
(if you did not exist, you would need to be invented)

#if_god_removes_jeremy_then_nevergrad_dies

[jrapin]

The distribution seems to be the one expected

In [13]: %cpaste -q
import numpy as np
import nevergrad as ng
import collections
param = ng.p.TransitionChoice(range(10), repetitions=100000)
param.set_standardized_data(np.random.normal(size=param.dimension))
counts = collections.Counter(param.value)
--

In [14]: counts
Out[14]:
Counter({0: 9964,
         4: 9936,
         9: 10254,
         6: 10013,
         8: 10001,
         7: 10002,
         2: 9811,
         3: 10097,
         5: 9918,
         1: 10004})