Added plotting function for unpaired proportional data

[bubbleli]

A working example is:

from scipy.stats import norm, bernoulli
import pandas as pd
control = bernoulli.rvs(0.3, loc=0, size=1000, random_state=12345)
test    = bernoulli.rvs(0.4, loc=0, size=1000, random_state=12345)
my_df   = pd.DataFrame({"control": control,
                            "test": test})
my_dabest_object = dabest.load(my_df, idx=("control", "test"), proportional=True)
print(my_dabest_object.mean_diff.plot())

[josesho]

Can you post the output as an image? thanks!!