Added some missing required traits to EC2 operations.
Resolved an attribute name issue in the SQS API model.

The SetQueueAttributesRequest structure listed "attributes"
as required but had a member with the name "Attributes". This
caused the param validator to raise an unhelp error and to fail
all `Aws::SQS::Client#set_queue_attributes_request` calls.

Fixes #74
Updated SQS model to remove empty example tags from the documentation.