Splice ./universe directory into ./

Manually merging:
- README.md: I added the description from universe/README.md into the heading of
  dotfiles/README.md.
- .envrc: dotfiles/.envrc was a superset of universe/.envrc
- .gitignore: Adding some of the ignored patterns from universe/.gitignore to
  dotfiles/.gitignore

Everything else here should be a simple rename.

universe/data_structures_and_algorithms/plot.py

@@ -1,9 +0,0 @@
-import numpy as np
-import matplotlib.pyplot as plt
-
-rng = np.random.RandomState(10)  # deterministic random data
-a = np.hstack((rng.normal(size=1000), rng.normal(loc=5, scale=2, size=1000)))
-_ = plt.hist(a, bins='auto')  # arguments are passed to np.histogram
-plt.title("Histogram with 'auto' bins")
-Text(0.5, 1.0, "Histogram with 'auto' bins")
-plt.show()