Update validator.rb and remove eventType

I was using this gem for a personal project and had to modify few stuff for better results.

**Changes**
1. `:eventType => 'completed'` was causing only the streamed videos to show up in search. So I removed it.
2. Updated the ORDERS array with correct camel case values. It was causing validation errors from Youtube.

Thanks for this gem, helped me a lot :+1: