* Fix missing validations on Signup
This commit fixes issue
https://github.com/plataformatec/devise/issues/4673
This removes `validate: false` from saving a record when `Trackable` is
in use.
* Add test case
* Add mongoid model
This reverts commit 43d0715238.
save() returns false only when validations failed. In this case, validations are
not performed. Therefore save() may never return a falsy value.
If save() fails, the appropriate exception is raised.
With certain ORMs, such as NoBrainer, save() never returns true/false, but
always raise an exception. This commit lift the incompatiblity.
Pat Allan