Refactor configuration file parsing

Now the time for importing the kitty.config module has been halved, from
16ms from 32ms on my machine. Also, the new architecture will eventually
allow for auto generating a bunch of python-to-C boilerplate code.

kittens/diff/highlight.py

@@ -159,13 +159,12 @@ def highlight_collection(collection: Collection, aliases: Optional[Dict[str, str
 
 
 def main() -> None:
-    from .config import defaults
     # kitty +runpy "from kittens.diff.highlight import main; main()" file
+    from .options.types import defaults
     import sys
     initialize_highlighter()
-    if defaults is not None:
-        with open(sys.argv[-1]) as f:
-            highlighted = highlight_data(f.read(), f.name, defaults.syntax_aliases)
-        if highlighted is None:
-            raise SystemExit('Unknown filetype: {}'.format(sys.argv[-1]))
-        print(highlighted)
+    with open(sys.argv[-1]) as f:
+        highlighted = highlight_data(f.read(), f.name, defaults.syntax_aliases)
+    if highlighted is None:
+        raise SystemExit('Unknown filetype: {}'.format(sys.argv[-1]))
+    print(highlighted)