Merge pull request vcr#535 from mrbrdo/fix_uninit_const_error

fix access to the EjectLinkedCassetteError error class

lib/vcr/linked_cassette.rb

@@ -60,7 +60,7 @@ def self.list(cassettes, linked_cassettes)
 
     # Prevents cassette ejection by raising EjectLinkedCassetteError
     def eject(*args)
-      raise EjectLinkedCassetteError,
+      raise Errors::EjectLinkedCassetteError,
         "cannot eject a cassette inserted by a parent thread"
     end