auth invalid should be logged 'warn' instead of 'error'

- also changed the logging of persistence error for better stack trace
- ignored mac os explorer autogenerated config file (did not use local ignore because a lot of people use macs)
- bumped version to 0.1.6
dummy commit: fixed semicolons

so that travis rebuilds the branch
Merge pull request #39 from zendesk/nherment/auth_invalid_should_warn_and_not_error

auth invalid should be logged 'warn' instead of 'error'