Added odd even sort algorithm in python

[prathimacode-hub]

trafficstars

I have included odd even sort algorithm in python.

[ericklarac]

Impl looks good, but could you add a comment explaining the algorithm?, e.g.

"""
Odd even sort algorithm ...
Time complexity: ...
Space complexity: ...
"""
def sort(array, compare=default_compare):
    ....

Also, add test cases and a link on the README.