Fix 'accept_filters' conf issue.
Merge pull request #9 from gsc-frank/conf_fix

Fix 'accept_filters' conf issue.
[#9] More clarification/simplification of factory

- Default value for `$config`; only pull config from SM if it is
  present.
- `isset` can be done on nested array keys without
  errors/warnings/notices.
Merge branch 'hotfix/9'

Close #9