added test situations for ignored return values
 Implemented processing of ignored returned values. Ignored errors have higher priority than ignored simple values, so lint will scream louder :)
 Added tests as well
 - Implemented config for lint. It can help to:
  1. Turn some checks off
  2. Add or remove checks for Initialisms and bad names of receivers
 - Removed `min-confidence` arg from golint syntax. Let's use config instead and `config` argument
 - Implemented 2 reporters that produce output in 2 formats:
  1. Plain text, like golint was doing it before
  2. XML checkstyle format
 - Linter problem now has name of the file
 - Run lint against lint and fixed the problems :)