contraMap and andThen on TypedSink/TypedSource
Merge pull request #892 from twitter/oscar-transform

contraMap and andThen on TypedSink/TypedSource
Tutorial 0-4 implemented for typed tutorial.
most of Tutorial5 (joins) implemented
working on getting Tutorial5 to do the right thing
working Tutorial 5
refactor comments
clean up comment
add comments, put 'TextLine()' into each case