Changed issues API call to prefix-based, fixes

Now the issues callback requires either 'all' - 'active' or 'inactive',
otherwise it just returns all.

Furthermore some more API fixes for 404-issues and not responding to
API requests if the user doesn't own the issue or the API key is
invalid to begin with.
Merge pull request #3 from SliceOLife/api-fix

Changed issues API call to prefix-based, fixes