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/string-reverse.py

@@ -0,0 +1,22 @@
+
+# swap :: Int -> Int -> [Char] -> IO ()
+def swap(ia, iz, xs):
+    # handle swap when ia == iz
+    assert ia <= iz
+    xs[ia], xs[iz] = xs[iz], xs[ia]
+    
+
+# reverse :: [Char] -> IO ()
+def reverse(xs):
+    ia = 0
+    iz = len(xs) - 1
+
+    while ia <= iz:
+        swap(ia, iz, xs)
+        ia += 1
+        iz -= 1
+
+x = list("superduperpooper")
+reverse(x)
+print(x)
+print("Tests pass")