Post merge fixes.
Cleanup code.

Remove obsolete codes and some obsolete TODOs.
Some performance improvements for comparing two vectors.
Add Easylogging++ as logging library for barn-agent.

As barn-agent logs get mixed together it can be hard to distinguish one
agent from another. Need to prefix log messages with the service_name that
the agent is reporting.
It appears Easylogging++ (http://easylogging.org/) is the simplest logging
library to solve this.

Also moved barn_conf to params.h where it seems more natural and stops the
circular dependence of barn-agent.h with other header files.
Merge pull request #21 from soundcloud/conor/list_iteraction_improvements

Conor/list iteraction improvements