Add ability for matplotlib_venn to take in multisets as parameters

[alexanderwhatley]

I've been using your package for a while, and recently I tried to draw a 3 way Venn Diagram, except that all three of the sets I had had duplicate elements. It would be possible to use either of the current APIs to draw the diagram, but it would be quite tedious either way, as I would either have to enumerate the duplicate elements or something like that if I were to use the list of sets, or I would have to compute 7 different numbers. Therefore, I propose allowing the user to enter a list of multisets (collections.Counter) as input parameters as well. An example is as follows:

from collections import Counter from matplotlib_venn import venn2, venn3 import matplotlib.pyplot as plt a = Counter([1,1,1,2,2,3,4]) b = Counter([1,1,2,4,5]) c = Counter([2,2,3,3,4,4,5,5,5,5,6]) venn_1 = venn2(subsets = [a,b], set_labels = ["a", "b"]) plt.show() venn_2 = venn3(subsets = [a,b,c], set_labels = ["a", "b", "c"]) plt.show()

[konstantint]

Thanks! I incorporated those changes in the code, however I cherry-picked and heavily edited your commit, and it seems that github did not recognize it as a pull request merge any more. FYI, things I changed:

• Avoided all the empty-line changes that were apparently suggested by your IDE.
• Added relevant doctests. Even tiny changes deserve those, I believe.
• Rewrote your modification with a bit less code duplication. After all, both set and Counter objects support &, | and - operations, the only difference is in how you compute the cardinality of a multiset-Counter.