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.

data_structures_and_algorithms/inflight-entertainment.py

@@ -0,0 +1,35 @@
+# possible :: Int -> [Int] -> Bool
+def possible(flight_duration, film_durations):
+    seeking = set()
+
+    for x in film_durations:
+        if x in seeking:
+            return True
+        else:
+            seeking.add(flight_duration - x)
+
+    return False
+
+
+should = [
+    (10, [1, 9, 8, 8, 8]),
+    (10, [1, 9]),
+    (10, [1, 9, 5, 5, 6]),
+    (1, [0.5, 0.5]),
+    (1, [0.5, 0.5]),
+]
+
+for a, b in should:
+    print("Testing: %s %s" % (a, b))
+    assert possible(a, b)
+
+shouldnt = [
+    (10, [1, 10, 1, 2, 1, 12]),
+    (1, [0.25, 0.25, 0.25, 0.25]),
+    (5, [1, 2, 2]),
+]
+for a, b in shouldnt:
+    print("Testing: %s %s" % (a, b))
+    assert not possible(a, b)
+
+print("Tests pass")