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.
Dropped rbx support from build matrix
Added Ruby 2.1.1 to the build matrix
Explicitly added bundler caching to travis build
Bumped version to v0.7.0