Add parquet-scrooge sources
Add parquet scrooge module to aggregate project so that its tests are run on the CI
Make parquet-scrooge 2.10 only
Add parquet-scrooge to travis.yml
rm scala 2.9 parquet-scrooge tests from travis.yml
Outer join handles case when both are empty

- If we are doing an outer join (K, A) x (K, B) by itself then it makes sense to assume that either A or B must exist for every key, but when composed with subsequent joins it is possible to get a key for which both A and B would be empty and the correct interpretation is to return an empty iterator (previously would do (None, None))
Merge pull request #1065 from aposwolsky/develop

Outer join handles case when both are empty
Merge pull request #1064 from twitter/alexlevenson/parquet-scrooge

Add parquet-scrooge sources
Bump to 0.12.0rc4