Add !behavior command

[zpatrick]

The name 'behavior' is probably too overloaded; should find a different one: trigger, function, etc.

Add a new !behavior command that will manage behavior objects.
A behavior has a pattern (probably regex) that will be ran against each message.
When the pattern matches, the behavior's function will execute.
Like aliases, we will want to allow templating in the function string.

!behavior add: Adds a new behavior object

!behavior add [--disabled] NAME PATTERN FUNCTION

!behavior ls: Lists behaviors

!behavior ls [--count=10] [--ascending]

!behavior rm: Remove a behavior

!behavior rm NAME

!behavior enable: Enable a behavior

!behavior enable NAME

!behavior disable: Disable a behavior

!behavior disable NAME

A simple example would be saying "hello" whenever someone else does:

user: !behavior add Welcome "[Hh]ello" "!echo Hello!"

[nehayward]

I like the name Trigger or Funtionless