Check for the renamed metadata method on Mongoid >= 4.0.0.beta1
Use lambdas for the default_scope, a requirement on Mongoid >= 4.0.0.beta1
Update for some changes in the I18n paths for error messages in carrierwave 0.10.0.
Document#image_identifier actually should be blank and not exactly '' after removing the image.
Change gem spec to allow carrierwave 0.10.0, and create a new gemfile for carrierwave 0.9.0.
Ops, forgot to add the new gemfile on travis config file.
Merge branch 'rafaelgaspar-carrierwave-0.10.0' into mongoid4-and-carriewave0.10

* rafaelgaspar-carrierwave-0.10.0:
  Ops, forgot to add the new gemfile on travis config file.
  Change gem spec to allow carrierwave 0.10.0, and create a new gemfile for carrierwave 0.9.0.
  Document#image_identifier actually should be blank and not exactly '' after removing the image.
  Update for some changes in the I18n paths for error messages in carrierwave 0.10.0.