Add a new recap plugin

This tracks all messages in a channel and when called replays the most
recent messages. This can be useful if someone just joined a channel and
wants to know what is going but not have to ask everyone.
Add a simple url tracker plugin

This tracks all messages which contain a url. Then on command will
replay those last few messages back.

This also adds a way to halt if a plugin fails to load.
Merge pull request #5 from n3world/urlTracker

Add a simple url tracker plugin
Merge pull request #7 from n3world/recap

Add a new recap plugin
Fixing typo in example config
Adding welcome params to config exxample
Adding an app.js wrapper to make AppFog happy