[spec] make it possible to use base check as a stub

we need a check method, and we add it to possible watchers you can request

lib/nerve/service_watcher/base.rb

@@ -57,6 +57,9 @@ def catch_errors(&block)
         end
       end
     end
+
+    CHECKS ||= {}
+    CHECKS['base'] = BaseServiceCheck
   end
 end
 

spec/factories/check.rb

@@ -1,6 +1,6 @@
 FactoryGirl.define do
   factory :check, :class => Hash do
-    type       'tcp'
+    type       'base'
     timeout    0.2
     rise       3
     fall       2

spec/factories/service.rb

@@ -4,7 +4,9 @@
     instance_id        'public_hostname.example.com'
     host               'localhost'
     port               3000
+    reporter_type      'base'
     checks             { create_list(:check, checks_count) }
+    check_interval     nil
 
     trait :zookeeper do
       reporter_type    'zookeeper'