Removing TestHelper from FeedService tests.

This removes the overhead imprint.

Tests run at quick speed:

$ rake test:file[test/services/feed_service_test.rb]
test/services/feed_service_test.rb
Rack::File headers parameter replaces cache_control after Rack 1.5.
Run options: --seed 41627

.....

Finished tests in 0.015902s, 314.4225 tests/s, 377.3070 assertions/s.

test/services/feed_service_test.rb

@@ -3,8 +3,6 @@
 require 'mocha/setup'
 
 describe FeedService do
-  include TestHelper
-
   describe "#find_or_create!" do
     let(:service)       { FeedService.new(target_feed) }
     let(:existing_feed) { mock }