New Task API

As discussed on gitter:

Instead of writing `tasks.call('LoggingTasks', 'log', 'Hello World')` you can now just write `LoggingTasks.log('Hello World')`.

Old code should be 100% compatible as long as you add `TaskHandler` as a superclass for everything in your tasks folder.

See `Readme.md` for details.

*Note: this pull request currently depends on #28 though it might be possible to use it independently*