Various code modifications.

The resource_path is kept clean by being regenerated for every AWS call.
Upgrade to AWS SQS 2012-11-05.
Add get_queue_url().
Add get_all_queue_attributes().
Support for deprecated use of queue name in the queue parameter.
The real AWS error message is extracted. Function check_error() is obsoleted.
POD documentation overhaul.
Updates to all test cases.
Test cases create their own test queues and delete them after script ends.
Test cases also check for emitted warn from the code.

To run the test cases, I recommend parallel execution.

    AWS_PUBLIC_KEY=blah_blah_blah \
    AWS_SECRET_KEY=blah_blah_blah \
      prove -j 8 t