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/java/Main.java

@@ -1,6 +0,0 @@
-public class Main {
-  public static void main(String[] args) {
-    System.out.println(System.getProperty("java.class.path"));
-    System.out.println(Another.whatis());
-  }
-}