Added FakeQueue to spec/spec_helper.rb

Added/Tested Impressionist::Consumer, which is responsible for popping callable
objects out of queue and calling call on them.
Added/Tested Impressionist::Subscriber
Added/Tested Impressionist::Consumer#call as ActiveSupport::Notifications calls
+call+ when an object is passed to subscribe method rather than a block of code

It now creates a new instance of Impressionist::Consumer#processor passing whatever
is received during the +call+ method. This is most probably to be a payload of a subscription.
Added/Tested Impressionist::BorderForce which saves impressions based on
given constraints, unique filters.
Fixed typo
Added indentation
Added impressionable_|type|id to Impressionist::Minion::Instrumentation