Support for regression tasks or issue an error while fitting real-valued 'y'

[FelSiq]

Is your feature request related to a problem? Please describe.
Support for regression tasks (real valued 'y'), or at least issue an error while fitting real-valued 'y'.

Describe the solution you'd like
Inspired by #92, I would like to request a solution for the scenario where the user fits a real-valued 'y'. The main solution is, of course, correctly support these type of data using some proposed solution available in the scientific literature.

Simple solutions, like the 'y' discretization, can be possible.

Describe alternatives you've considered
An alternative temporary solution would be to raise an error when the user fits a real-valued y' (pretty much like the Sklearn Classifiers do). That can potentially break existing code using the Pymfe though.

Additional context
None.