Overhaul docs.

- Document backporting
- Reference the cPython dev docs for everything else.
- Test docs and package summary.
diff --git a/.gitignore b/.gitignore
index 8502ec1..93d1155 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,6 @@
 .*.swp
 AUTHORS
 ChangeLog
+.eggs
+README.saved
+README.html