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/advent-of-code/day_5.ex

@@ -1,50 +0,0 @@
-defmodule Interpretter do
-  def interpret_param({mode, x}, xs) do
-    case mode do
-      :positional -> Enum.at(xs, x)
-      :immediate  -> x
-    end
-  end
-
-  # Perhaps I can model the intepretter after Forth and make it a stack-based
-  # interpretter with an emphasis on debugability, introspection.
-  def interpret(i, xs) do
-    stack = []
-    op = Enum.at(xs, i)
-
-    # map instructions into an intermediate representation (i.e. IR) where the
-    # opcodes are mapped into atoms and the arguments are mapped into references
-    # or literals.
-
-    instructions =
-      %{'01' => :add,
-        '02' => :multiply,
-        '03' => :input,
-        '04' => :output,
-        '05' => :jump_if_true,
-        '06' => :jump_if_false,
-        '07' => :less_than,
-        '08' => :equal_to,
-        '99' => :return}
-
-    case xs do
-      [:add, a, b, {:positional, out} | rest] ->
-        a = interpret_param(a, xs)
-        b = interpret_param(b, xs)
-        Interpretter.interpret(i + 3, List.insert_at(xs, out, a + b))
-
-      [:multiply, a, b, {:positional, out} | rest] ->
-        a = interpret_param(a, xs)
-        b = interpret_param(b, xs)
-        Interpretter.interpret(i + 3, List.insert_at(xs, out, a * b))
-
-      [:input, a | rest] -> nil
-      [:output, a | rest] -> nil
-      [:jump_if_true, a, b | rest] -> nil
-      [:jump_if_false, a, b | rest] -> nil
-      [:less_than, a, b, out | rest] -> nil
-      [:equal_to, a, b, out | rest] -> nil
-      [:return | _rest] -> nil
-    end
-  end
-end