Fix test suite crashes stemming from 9542529 on Travis

lib/paper_trail/version_concern.rb

@@ -7,13 +7,17 @@ module PaperTrail
     included do
       belongs_to :item, :polymorphic => true
 
-      if PaperTrail::VersionAssociation.table_exists?
+      # Need to inspect inside of a Proc so that tests pass even when DB is not initialized
+      # such as when we run on Travis (there won't be a db in `test/dummy/db/`)
+      if lambda { PaperTrail::VersionAssociation.table_exists? }
         has_many :version_associations, :dependent => :destroy
       end
 
       validates_presence_of :event
 
-      attr_accessible :item_type, :item_id, :event, :whodunnit, :object, :object_changes, :transaction_id, :created_at if PaperTrail.active_record_protected_attributes?
+      if PaperTrail.active_record_protected_attributes?
+        attr_accessible :item_type, :item_id, :event, :whodunnit, :object, :object_changes, :transaction_id, :created_at
+      end
 
       after_create :enforce_version_limit!