Support for explicit AWS credentials (with same options as yum-s3-plugin)
Fixed test
Merge pull request #23 from paulegan/set_credentials

Support for explicit AWS credentials
Added YumTestCase
Use prereposetup_hook instead of postreposetup_hook.

If urlgrabber has parallel_wait() and repo has async enabled, then
doSetup will try to retrieve metadata before the "postreposetup" hook is
called.
Updated README