Documentation issues for v2.0.x

[amauryt]

Thank you for the update to this add-on and for ember-bootstrap in general. However, while updating my app I noticed two small issues with the documentation:

1. The example on the README seems to be for ember-bootstrap-changeset-validations as it uses the changeset helper.
2. Version 1.x had a nice feature that in certain cases when the cp-validation included presence: true, then it would mark the form element as required (see this line). Given that this seem to not be the case anymore, I think it should have been documented as a breaking change; albeit it would be nice to have this feature back.

[jelhan]

The example on the README seems to be for ember-bootstrap-changeset-validations as it uses the changeset helper.

Also noticed that one and opened #62.