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/find-duplicate-optimize-for-space-beast.py

@@ -1,56 +0,0 @@
-import unittest
-
-
-################################################################################
-# Solution
-################################################################################
-def find_duplicate(xs):
-    self_ref_count = 0
-    for i in range(len(xs)):
-        if xs[i] == i + 1:
-            self_ref_count += 1
-    hops = len(xs) - 1 - self_ref_count
-    current = xs[-1]
-    while hops > 0:
-        current = xs[current - 1]
-        hops -= 1
-    return current
-
-
-################################################################################
-# Tests
-################################################################################
-class Test(unittest.TestCase):
-    # TODO: Debug why this fails.
-    def test_darren_from_interview_cake(self):
-        actual = find_duplicate([4, 1, 8, 3, 2, 7, 6, 5, 4])
-        expected = 4
-        self.assertEqual(actual, expected)
-
-    def test_just_the_repeated_number(self):
-        actual = find_duplicate([1, 1])
-        expected = 1
-        self.assertEqual(actual, expected)
-
-    def test_short_list(self):
-        actual = find_duplicate([1, 2, 3, 2])
-        expected = 2
-        self.assertEqual(actual, expected)
-
-    def test_last_cycle(self):
-        actual = find_duplicate([3, 4, 2, 3, 1, 5])
-        expected = 3
-        self.assertEqual(actual, expected)
-
-    def test_medium_list(self):
-        actual = find_duplicate([1, 2, 5, 5, 5, 5])
-        expected = 5
-        self.assertEqual(actual, expected)
-
-    def test_long_list(self):
-        actual = find_duplicate([4, 1, 4, 8, 3, 2, 7, 6, 5])
-        expected = 4
-        self.assertEqual(actual, expected)
-
-
-unittest.main(verbosity=2)