Removes outdated 'require virtus'

‘virtue’ is no longer used
Removes #home_url test from #initialize describe

#home_url tests should not be nested within the #initialize describe
block.
Tests config.return_as_active_resource default value
Adds tests for Config#has_home?
Removes unnecessary config variable

A config is already declared
Adds tests for Config#to_hash
Do not rails host not set error in Config#to_hash

Invoking Config#raise_if_host_not_set method in Config#to_hash is
unnecessary. This method is raised within Config#home_url, which is
invoked within Config#to_hash.