Second round of improvements for hygdrop

Following things are done in this PR

- Port hygdrop for 0.9.12, replace `foreach` with `for`
- Handle broken test cases which are related to network
- Implement HygdropREPL with specific customization for the bot
- Better error handling in code execution and exception/traceback tracking.
- Long and multiline output/source and exceptions are pasted to refheap.com and URL is pasted to IRC.

Probably the *bro* messages by hygdrop can be improved if needed.