Feature request

Summary

With the new style of plotting (after version 1.5), you cannot distinguish the bars on plt.hist. Take for example the old way:

import matplotlib.pyplot as plt
import random

l_n = []
for _ in range(2000):
    l_n.append(random.betavariate(5, 25))

with plt.style.context('classic'):
    plt.hist(l_n, bins=20)
    plt.show()

Unfortunately, I cannot upload images. Nevertheless, you can see the bars. Now, this:

plt.hist(l_n, bins=20)
plt.show()

You only see the silhouette of the histogram, not the bars. An easy way to solve this:

plt.hist(l_n, bins=20, edgecolor='w')
plt.show()

edgecolor='w' would be the default option (I would prefer white because it looks good with all the styles). What do you think?

By the way, if you want to compare with other software, I think all of them show bars. And a quick search shows...

Matplotlib version

• Operating system: Ubuntu 16.04.5 LTS
• Matplotlib version: 3.0.1
• Matplotlib backend (print(matplotlib.get_backend())): Qt5Agg
• Python version: 3.6.6
• Jupyter version (if applicable): 7.1.1
• Other libraries:
• How I installed matplotlib: conda