remove duplicate LookupJoin - use Scalding's.

[sritchie]

#596 already did this, but that branch has merge conflicts. Deletes our implementation and tests and relies on the Scalding version of LookupJoin.

The dependencies mentioned in #596 are all complete.

r? @johnynek

[ianoc]

Looks like build is failing?

[info] - should compute correct statistics *** FAILED ***
[info]   java.lang.NullPointerException:
[info]   at com.twitter.summingbird.scalding.ScaldingLaws$$anonfun$1$$anonfun$apply$mcV$sp$12.apply$mcV$sp(ScaldingLaws.scala:605)
[info]   at com.twitter.summingbird.scalding.ScaldingLaws$$anonfun$1$$anonfun$apply$mcV$sp$12.apply(ScaldingLaws.scala:573)
[info]   at com.twitter.summingbird.scalding.ScaldingLaws$$anonfun$1$$anonfun$apply$mcV$sp$12.apply(ScaldingLaws.scala:573)
[info]   at org.scalatest.Transformer$$anonfun$apply$1.apply$mcV$sp(Transformer.scala:22)
[info]   at org.scalatest.OutcomeOf$class.outcomeOf(OutcomeOf.scala:85)
[info]   at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)
[info]   at org.scalatest.Transformer.apply(Transformer.scala:22)
[info]   at org.scalatest.Transformer.apply(Transformer.scala:20)
[info]   at org.scalatest.WordSpecLike$$anon$1.apply(WordSpecLike.scala:953)
[info]   at org.scalatest.Suite$class.withFixture(Suite.scala:1122)

[johnynek]

weird. This is the line with the NPE:

https://github.com/twitter/summingbird/blob/develop/summingbird-scalding-test/src/test/scala/com/twitter/summingbird/scalding/ScaldingLaws.scala#L605

It looks like that should only happen if the job does not run. Restated.

[sritchie]

Strange. @johnynek @ianoc merge or investigate more?

[ianoc]

If its green I think we are good to go. In that maybe we want to check sometime if this re-occurs, but seems unrelated to change