Add vhost name based activation strategy

The activation strategy that will use the Virtual Host (vhost) server name
used in the request to decide if the feature is active or not.
This strategy can be useful when given service instance is available through
two different Virtual Host names (vhosts like www.example.com and
beta.example.com) each with different features enabled.
By the way test dependencies update and unification.
Revert "Log failures when persisting new feature state using the FileBasedStateRepository (fixes #87)"

This reverts commit cf07f38066e49e7cad209c5eebdf4fce031bf46a.
VhostNameActivationStrategy -> ServerNameActivationStrategy