Added a method to enable bulk prediction
Added unit tests for bulk prediction in MatrixFactorizationModel
Removed unnecessary blank line
Added python binding for bulk recommendation
Added serializing method for Rating object
Added Rating deserializer
Added predictAll python function to MatrixFactorizationModel
Merge branch 'master' into MatrixFactorizationModel-fix
Merge pull request #328 from falaki/MatrixFactorizationModel-fix

SPARK-1012: DAGScheduler Exception Fix

Added a predict method to MatrixFactorizationModel to enable bulk prediction. This method takes and RDD[(Int, Int)] of users and products and return an RDD with a Rating element per each element in the input RDD.

Also added python bindings to the new bulk prediction methods to address SPARK-1011 issue.

This is ready to be merged now.