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/linked-list-cycles.py

@@ -1,88 +0,0 @@
-import unittest
-
-
-################################################################################
-# Solution
-################################################################################
-def contains_cycle(x):
-    if not x:
-        return False
-    elif not x.next:
-        return False
-
-    a = x
-    b = x.next
-
-    while b.next:
-        if a == b:
-            return True
-
-        a = a.next
-        b = b.next.next
-
-    return False
-
-
-################################################################################
-# Tests
-################################################################################
-class Test(unittest.TestCase):
-    class LinkedListNode(object):
-        def __init__(self, value, next=None):
-            self.value = value
-            self.next = next
-
-    def test_linked_list_with_no_cycle(self):
-        fourth = Test.LinkedListNode(4)
-        third = Test.LinkedListNode(3, fourth)
-        second = Test.LinkedListNode(2, third)
-        first = Test.LinkedListNode(1, second)
-        result = contains_cycle(first)
-        self.assertFalse(result)
-
-    def test_cycle_loops_to_beginning(self):
-        fourth = Test.LinkedListNode(4)
-        third = Test.LinkedListNode(3, fourth)
-        second = Test.LinkedListNode(2, third)
-        first = Test.LinkedListNode(1, second)
-        fourth.next = first
-        result = contains_cycle(first)
-        self.assertTrue(result)
-
-    def test_cycle_loops_to_middle(self):
-        fifth = Test.LinkedListNode(5)
-        fourth = Test.LinkedListNode(4, fifth)
-        third = Test.LinkedListNode(3, fourth)
-        second = Test.LinkedListNode(2, third)
-        first = Test.LinkedListNode(1, second)
-        fifth.next = third
-        result = contains_cycle(first)
-        self.assertTrue(result)
-
-    def test_two_node_cycle_at_end(self):
-        fifth = Test.LinkedListNode(5)
-        fourth = Test.LinkedListNode(4, fifth)
-        third = Test.LinkedListNode(3, fourth)
-        second = Test.LinkedListNode(2, third)
-        first = Test.LinkedListNode(1, second)
-        fifth.next = fourth
-        result = contains_cycle(first)
-        self.assertTrue(result)
-
-    def test_empty_list(self):
-        result = contains_cycle(None)
-        self.assertFalse(result)
-
-    def test_one_element_linked_list_no_cycle(self):
-        first = Test.LinkedListNode(1)
-        result = contains_cycle(first)
-        self.assertFalse(result)
-
-    def test_one_element_linked_list_cycle(self):
-        first = Test.LinkedListNode(1)
-        first.next = first
-        result = contains_cycle(first)
-        self.assertTrue(result)
-
-
-unittest.main(verbosity=2)