Remove TODO.txt now that I found time to put in github issues.

TODO.txt

@@ -1,10 +0,0 @@
-TODOs in no particular order
-============================
-
- * Support group messaging
- * Refactor helpers.js into more files
- * Fix the type conversion hell I've gotten myself into
- * Min-ify js-deps into fewer files
- * Support attachments
- * Propose multi-device protos/protocol to upstream, support it here
- * Fix storage of sent messages/refactor UI a bit to show conversations, not messages