Removing duplicate methods for resource identifiers.

Previously resources, such as IAM::User might have methods such as

* User#name
* User#user_name

The duplicate methods from the data attributes are no longer going
to be added. These will drop off as the "dataMember" traits are
added to the resource definitions.
Sped up aws-sdk-resource unit tests.

The S3 file upload tests were very slow due to creating
large tempfiles on disk. Instead now, tempfiles are
created and their size is stubbed.
Added a functional test for resource has many enumeration.
Removed a pending test from a feature there is no plan to implement.
Added functional tests for resource hasOne and hasSome.