Better sample config; bug fixes

Provide better sample configuration for cli
Catch additional render errors
Bug fix - use correct method of allowing aria2 to set gid
Change API URL
Merge pull request #207 from tubedogg/prowl_bug_1-2-81

prowl Plugin - Change API URL
Try to make download plugin failure reasons more descriptive.
Pythonic
Merge pull request #206 from tubedogg/aria_bugfix_1-2-81

aria2 Plugin - Better sample config; bug fixes