Changed Janus to #{robot.name}

There are errors saying that robot is not a variable

It seems like this shouldn't be happening when reading the Lita Doc
Removed hard coded robot name

Greetings to the bot is now dependent on what robot.name is set to.
This can be configured in the lita_config.rb file under Changebot

Tests have been adjusted with a few new ones written.
Added an additional test

There were no tests before that tested whether the bot should not respond unless its being addressed.