Merge pull request #968 from twitter/ref_trans_typedpipe

Make TypedPipe immutable
Generalize handling of merged TypedPipes
Add Ian's suggested comment
do not inherit from FileSource in LzoTraits
Merge pull request #976 from amatsukawa/remove_file_source_from_LzoTraits

Do not inherit from FileSource in LzoTraits
Merge pull request #975 from twitter/fix_typed_merge

Generalize handling of merged TypedPipes
Merge with develop
Add Kmeans test to execution