Renamed com.snowplowanalytics (event type) to com_snowplowanalytics, so that
Avro knows not to ignore the namespace that it is a part of
(com.snowplowanalytics.storage.avro... etc.)

Added files from Alex's hack to enable Avro SBT to compile IDL files

Created first IDL file: SnowPlowVersion
Merge branch 'feature/avro' of https://github.com/snowplow/snowplow into feature/avro