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/dijkstra-shortest-path.py

@@ -1,48 +0,0 @@
-from collections import deque
-from heapq import heappush, heappop
-from fixtures import weighted_graph
-
-
-def put(t, x, xs):
-    if t == 'stack':
-        return xs.append(x)
-    if t == 'queue':
-        return xs.append(x)
-    if t == 'priority':
-        return heappush(xs, x)
-
-
-def pop(t, xs):
-    if t == 'stack':
-        return xs.pop()
-    if t == 'queue':
-        return xs.popleft()
-    if t == 'priority':
-        return heappop(xs)
-
-
-# shortest_path :: Vertex -> Vertex -> Graph -> [Vertex]
-def shortest_path(a, b, g):
-    """Returns the shortest path from vertex a to vertex b in graph g."""
-    t = 'priority'
-    xs = []
-    seen = set()
-    # Map(Weight, [Vertex])
-    m = {}
-
-    put(t, (0, [a], a), xs)
-
-    while xs:
-        w0, path, v = pop(t, xs)
-
-        seen.add(v)
-        if v == b:
-            m[w0] = path
-        for w1, x in g.get(v):
-            if x not in seen:
-                put(t, (w0 + w1, path + [x], x), xs)
-
-    return m
-
-
-print(shortest_path('a', 'f', graph_a))