Tag release v1.0.0.pre.7

References: #14, #17

* Upgrading - Aws::Record - This release includes changes to validation and
  to the `#save` and `#save!` methods. With this release, the validation hooks
  in `Aws::Record::Attribute` have been removed. Additionally, `#save` will
  resume raising exceptions on client errors. However, `#save` and `#save!`
  will attempt to call `#valid?` if defined on the model, and will return false
  or raise as appropriate if that method is defined and returns false.

  As a part of this change, we've removed the built in `#valid?` and `#errors`
  methods. If you were a user of those, consider bringing your own validation
  library such as `ActiveModel::Validations`.

* Issue - Aws::Record - Removes `#valid?` and `#errors` methods, which caused a
  conflict with the ability to bring your own validation library such as
  `ActiveModel::Validations`. Added tests as an example and to test
  compatibility.