Use smaller broadcast and plyr instead of Matrix
Matrix package takes around 2s to load and slows down unit tests.
Merge branch 'master' of github.com:amplab/SparkR-pkg into unit-tests
Update travis to install plyr
Merge pull request #10 from shivaram/unit-tests

Make unit tests a bit more faster
Search rLibDir in worker before libPaths
This ensures we pick up the SparkR intended and not an older version
installed on the same machine
Merge pull request #11 from shivaram/master

Search rLibDir in worker before libPaths
Add isCached field (inside an env) and unpersist().
Minor inline comment style fix.
Add `isCheckpointed` field and checkpoint().
First cut at PipelinedRDD.

- Add constructor & getJRDD logic
- Use PipelinedRDD in lapply and lapplyPartitionsWithIndex
Put serialized field inside env for both RDD and PipelinedRDD.