Fix a bug in LookupJoin
remove commented code
Merge pull request #579 from twitter/fix-lookup

Fix a bug in LookupJoin
Update README.md
Removes closures in TypedPipe, adds Empty
Some cleanups
Some cleanups
Add a type
add a transient
Merge pull request #586 from twitter/typed-pipe-closures

Removes closures in TypedPipe, adds Empty