[SPARK-2433][MLLIB] fix NaiveBayesModel.predict

This is the same as apache#463 , which I forgot to merge into branch-0.9.

Author: Xiangrui Meng <meng@databricks.com>

Closes apache#1453 from mengxr/nb-transpose-0.9 and squashes the following commits:

bc53ce8 [Xiangrui Meng] fix NaiveBayes

Author: mengxr

python/pyspark/mllib/classification.py

@@ -84,7 +84,7 @@ class NaiveBayesModel(object):
     - pi: vector of logs of class priors (dimension C)
     - theta: matrix of logs of class conditional probabilities (CxD)
 
-    >>> data = array([0.0, 0.0, 1.0, 0.0, 0.0, 2.0, 1.0, 1.0, 0.0]).reshape(3,3)
+    >>> data = array([0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 2.0, 1.0, 1.0]).reshape(3,3)
     >>> model = NaiveBayes.train(sc.parallelize(data))
     >>> model.predict(array([0.0, 1.0]))
     0
@@ -98,7 +98,7 @@ def __init__(self, pi, theta):
 
     def predict(self, x):
         """Return the most likely class for a data vector x"""
-        return numpy.argmax(self.pi + dot(x, self.theta))
+        return numpy.argmax(self.pi + dot(x, self.theta.transpose()))
 
 class NaiveBayes(object):
     @classmethod