Better description to EmailsOnPush service

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/project_services/emails_on_push_service.rb

@@ -25,7 +25,7 @@ class EmailsOnPushService < Service
   end
 
   def description
-    'Send emails to recipients on push'
+    'Email the commits and diff of each push to a list of recipients.'
   end
 
   def to_param