src/conf.py: Plugin isn't important plugin

See https://github.com/ProgVal/Limnoria/pull/677#issuecomment-44134309 & https://github.com/ProgVal/Limnoria/pull/677#issuecomment-44140276 .
Merge pull request #678 from Mkaysi/patch-1

src/conf.py: Plugin isn't important plugin