Bang in the methods discard and undiscard

[celsoMartins]

Hey. Congratulations for the great job. I've started to use it today and seems to be a useful tool.

But the methods "discard" and "undiscard", following the rails patterns, should not have a bang, since it changes the database?

discard!
undiscard!

[jhawthorn]

Methods don't need to have a bang to change the database (model.save exists), but they do to raise an error on failing (like model.save!).

We've just added discard! and undiscard! in #17 🎉, but there hasn't yet been a release yet with that change.

Hope that helps!

[lucabob]

@jhawthorn Any chance you could do a release, so that these methods are included?