Better error handling

[taylorthurlow]

Currently components add errors to an @errors instance variable. This makes it so methods in components which fail in one way or another still need to return a value in order to prevent actual exceptions.

To handle this, real errors should be raised (something like ComponentError), and the #process method should be able to catch them and log them. This will make error control flow easier, while still allowing execution to continue to other components.