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/nth-fibonacci.py

@@ -1,59 +0,0 @@
-import unittest
-
-
-################################################################################
-# Solution
-################################################################################
-def fib(n):
-    """This should be accomplishable in O(1) space."""
-    if n in {0, 1}:
-        return n
-    a = 0  # i = 0
-    b = 1  # i = 1
-    for x in range(2, n + 1):
-        result = a + b
-        a = b
-        b = result
-    return result
-
-
-################################################################################
-# Tests
-################################################################################
-class Test(unittest.TestCase):
-    def test_zeroth_fibonacci(self):
-        actual = fib(0)
-        expected = 0
-        self.assertEqual(actual, expected)
-
-    def test_first_fibonacci(self):
-        actual = fib(1)
-        expected = 1
-        self.assertEqual(actual, expected)
-
-    def test_second_fibonacci(self):
-        actual = fib(2)
-        expected = 1
-        self.assertEqual(actual, expected)
-
-    def test_third_fibonacci(self):
-        actual = fib(3)
-        expected = 2
-        self.assertEqual(actual, expected)
-
-    def test_fifth_fibonacci(self):
-        actual = fib(5)
-        expected = 5
-        self.assertEqual(actual, expected)
-
-    def test_tenth_fibonacci(self):
-        actual = fib(10)
-        expected = 55
-        self.assertEqual(actual, expected)
-
-    def test_negative_fibonacci(self):
-        with self.assertRaises(Exception):
-            fib(-1)
-
-
-unittest.main(verbosity=2)