Merge pull request #15 from lisahua/develop

Add PMMLEncogNN Test cases
Merge remote-tracking branch 'upstream/develop' into develop

1. add Spark LR trainer
2. add Mahout LR and NN trainer
3. add Mahout LR and NN PMMLAdapter as well as MLBuilder
change akka version from 2.1.1 to 2.2.3