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/largest-stack.py

@@ -1,107 +0,0 @@
-import unittest
-
-
-class Stack(object):
-    def __init__(self):
-        """Initialize an empty stack"""
-        self.items = []
-
-    def push(self, item):
-        """Push a new item onto the stack"""
-        self.items.append(item)
-
-    def pop(self):
-        """Remove and return the last item"""
-        # If the stack is empty, return None
-        # (it would also be reasonable to throw an exception)
-        if not self.items:
-            return None
-
-        return self.items.pop()
-
-    def peek(self):
-        """Return the last item without removing it"""
-        if not self.items:
-            return None
-        return self.items[-1]
-
-
-class MaxStack(object):
-    # Implement the push, pop, and get_max methods
-    def __init__(self):
-        self.m = Stack()
-        self.stack = Stack()
-
-    def push(self, item):
-        if self.m.peek() is None:
-            self.m.push(item)
-        elif item >= self.m.peek():
-            self.m.push(item)
-        self.stack.push(item)
-
-    def pop(self):
-        x = self.stack.pop()
-        if x == self.m.peek():
-            self.m.pop()
-        return x
-
-    def get_max(self):
-        return self.m.peek()
-
-
-################################################################################
-# Tests
-################################################################################
-class Test(unittest.TestCase):
-    def test_stack_usage(self):
-        max_stack = MaxStack()
-
-        max_stack.push(5)
-
-        actual = max_stack.get_max()
-        expected = 5
-        self.assertEqual(actual, expected)
-
-        max_stack.push(4)
-        max_stack.push(7)
-        max_stack.push(7)
-        max_stack.push(8)
-
-        actual = max_stack.get_max()
-        expected = 8
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.pop()
-        expected = 8
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.get_max()
-        expected = 7
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.pop()
-        expected = 7
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.get_max()
-        expected = 7
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.pop()
-        expected = 7
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.get_max()
-        expected = 5
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.pop()
-        expected = 4
-        self.assertEqual(actual, expected)
-
-        actual = max_stack.get_max()
-        expected = 5
-        self.assertEqual(actual, expected)
-
-
-unittest.main(verbosity=2)