Transferred from: dyweb/Ayi#59

• allow user specify log filtering in command line argument. i.e. allow=a.git,a.web
• allow user specify log filtering in config file

allow:
  - a.git
  - a.web

Ref

• https://github.com/cihub/seelog provides a lot of example for filtering and logrus also has an issue about this Configuration file support sirupsen/logrus#142