Change Ensemble 'classifiers' attribute to 'estimators' and use 'classifiers/regressors' as properties.

[dvro]

Ensemble objects should work with both classifiers and regressors, changing only the output mode.

[sfrodrigues]

Any progress on this?

[thypad]

We're working on a new version of the library that will also support regressors, and it will be released in the next few weeks.