Add avro support into Scalding as a module.
Merge branch 'develop' of https://github.com/twitter/scalding into scalding-avro-module
Keeping up to date with develop branch
Fixed 2.10 issue with HadoopSchemeInstance (doesn't work with AvroSource somehow)
Fixed helper functions, added license info and README.
Added some better apply functions in UnpackedAvroSource per Oscar's suggestion.
Merge pull request #525 from ccsevers/scalding-avro-module

New module for Avro support