Associative array
Add prototype conversation tree script
Utility.
Fixes and tests
Becuase regular expressions
Working dialogues
Merge branch 'npc-lua'
Store the current Lua thread on each yield.

I don't think there's any good reason to start a coroutine in an event handler
and then call the dialogue functions from that coroutine, but better safe than sorry.
Explanations and error handling
Index dialogue choices starting at 1
Proper way to handle GC of coroutines
Remove old NPC definition system
Merge pull request #13 from staven/master

Basic NPC dialogue tree stuff thing