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/trickling-water.py

@@ -1,38 +0,0 @@
-class Node(object):
-    def __init__(self, value, children=[]):
-        self.value = value
-        self.children = children
-
-
-################################################################################
-# Solution
-################################################################################
-def trip_time(node):
-    s = []
-    result = 0
-    s.append((node.value, node))
-    while s:
-        p, node = s.pop()
-        if not node.children:
-            result = max(result, p)
-        for x in node.children:
-            s.append((p + x.value, x))
-    return result
-
-
-################################################################################
-# Tests
-################################################################################
-tree = Node(
-    0,
-    children=[
-        Node(5, children=[Node(6)]),
-        Node(2, children=[
-            Node(6),
-            Node(10),
-        ]),
-        Node(3, children=[Node(2, children=[Node(11)])]),
-    ])
-
-assert trip_time(tree) == 16
-print("Tests pass!")