[SPARK-2429] [MLlib] Hierarchical Implementation of KMeans
Fix the tests of HierarchicalClusteringConf
Using 2-space indent in Java code, not 4-space indent
Fix the spell mistake
Add HierarchicalClusteringConf.toString
Split if sentence onto two lines
Unpersist the RDDs which is necessary no longer
Use `require` at HierarchicalClustering.validate, not if-sentence
Modify using not java.lang.Math but scala.math.abs
Fix the type mistakes
Modify how to broadcast the variable in order to find the closest cluster
Add a comment about the referenced paper
Change `ClusterTree` class to a private class
Fix the test about ClusterTree.getHeight()
Change HierarchicalClusteringConf class to a trait for HierarchicalClustering
Support the options of `train`
Fix PEP8 violations in the python code
Modify the python code in order to `predict` with Java API
Improve the performance to deal with sparce vectors
Fix PEP8 violations in the python code