general: add compat module and helper for easy backwards compatibiltity for pre-PIP dependencies

my.hypothesis: use hypexport as a proper PIP package + fallback

my/github/ghexport.py

@@ -1,6 +1,9 @@
 """
 Github data: events, comments, etc. (API data)
 """
+REQUIRES = [
+    'git+https://github.com/karlicoss/ghexport',
+]
 from dataclasses import dataclass
 from typing import Optional