Updated SBT configuration to use separate per-project .sbt files instead of one monolithic Build.scala
Added .gitattributes file to control how git clients manage line endings.  Hopefully, this will help with checkouts on Windows clients.
- com.gensler.scalavro.Union:
    - Updated to ensure that the underlyingConjunctionTag property's type is fully specified as TypeTag[Union.not[_]] instead of simply TypeTag[_]
    - Added some basic documentation
- com.gensler.scalavro.types.complex.AvroUnion: Some type clarifications, optimization
- com.gensler.scalavro.Union:
    - Updated to ensure that the underlyingConjunctionTag property's type is fully specified as TypeTag[Union.not[_]] instead of simply TypeTag[_]
    - Added some basic documentation
- com.gensler.scalavro.types.complex.AvroUnion: Some type clarifications, optimization