Revert commit 73723cdbc8

* Causing issues with virtual attributes and error messages (#277)
* Will need to come up with another solution than adding a check for setting an
attribute correctly.
Bump version to 1.5.6
Remove 'delegate_method' matcher

* See issue #252
Remove 'strong_parameters' matcher

* See issue #252
* Also changes bourne dependency into a development dependency
Remove 'have_sent_email' matcher

* See issue #252
Remove 'validate_format_of' matcher

* See issue #252
Remove 'query_the_database' matcher

* See issue #252
Remove 'respond_with_content_type' matcher

* See issue #252
Remove 'assign_to' matcher

* See issue #252
Bump version to 2.0.0
Add allow_nil option to the validate uniquness matcher
Support datetime columns in `validate_uniqueness_of.scoped_to`
Allow the use of %{attribute} or %{model} in i18n translations.

Fix a bug where shoulda was raising an exception, when a translation
in en.yml was modified to include %{attribute} or %{model}