Add ability to pass in redis object
Timeseries Widget: convert tick Enum to Arr for .last
Fixed logger so that it listens on pub sub events from the worker.

Before if relied on `FnordMetric.backend` which has been removed.
But since it accessed it in a thread, the thread just died and nothing more would happen.
Improved handling of channels in logger.
Removed unused variable.
Merge pull request #172 from tobiashm/logger

Fixed Logger module
Merge pull request #164 from anapsix/upstream-issue163

Timeseries Widget: convert tick Enum to Arr for .last
Merge pull request #151 from johnf/custom_redis

Add ability to pass in redis object