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/permutations.py

@@ -1,55 +0,0 @@
-class Node(object):
-    # ctor :: a -> [a] -> Node(a)
-    def __init__(self, value, children=[]):
-        self.value = value
-        self.children = children
-
-
-# is_leaf :: Node(a) -> Boolean
-def is_leaf(node):
-    return len(node.children) == 0
-
-
-# enumerate :: Node(a) -> Set(List(a))
-def enumerate(node):
-    current = []
-    result = []
-    q = []
-
-    q.append(node)
-
-    while q:
-        x = q.pop()
-        print(x.value)
-
-        for c in x.children:
-            q.append(c)
-
-        current.append(x.value)
-        print(current)
-
-        if is_leaf(x):
-            result.append(current)
-            print("Reseting current")
-            current = []
-
-    return result
-
-
-node = Node('root', [
-    Node('a', [
-        Node('b', [Node('c')]),
-        Node('c', [Node('b')]),
-    ]),
-    Node('b', [
-        Node('a', [Node('c')]),
-        Node('c', [Node('a')]),
-    ]),
-    Node('c', [
-        Node('a', [Node('b')]),
-        Node('b', [Node('a')]),
-    ])
-])
-
-print('----------')
-print(enumerate(node))