TODO

Some of the things I think should be done in case someone decides to help (in
no particular order):

- Add usefull logging to Pipeline. This should be done in a way that logs for a
  given pipeline are generated at the pipeline level itself, not at the module
  level. This means that modules should broadcast log messages to the pipeline
  instance (maybe using channels). Levelled logs would be great too and could
  use https://github.com/golang/glog
- Improve error reporting (can be done together with the popint above).
  Currently error messages do not give any indication of which module generated 
  which error message.
- Add more modules that can be used to do something usefull.
- Add configurations that do real work.
- Improve main file so it can be configured via flags (for instance, to set
  config to use). Also add flags to override specific module/pipeline
  configuration whenever it makes sense.
- Add support for modules to persist data. This could be used, for example, to
  allow a plugin to only proccess items that are relevant since the last time it
  ran.
- Improve code comments.
- Support connecting one pipeline to another.
- Add tests.