Finish HackMyCore reshaping.

Reintroduce HackMyCore, dropping the interim submodule, and reorganize
and improve tests.

src/core/default-options.coffee

@@ -0,0 +1,13 @@
+###
+Event code definitions.
+@module core/default-options
+@license MIT. See LICENSE.md for details.
+###
+
+module.exports =
+  theme: 'modern'
+  prettify: # ← See https://github.com/beautify-web/js-beautify#options
+    indent_size: 2
+    unformatted: ['em','strong']
+    max_char: 80, # ← See lib/html.js in above-linked repo
+    # wrap_line_length: 120, ← Don't use this