Clean up some comments.

ml/src/main/scala/spark/ml/GradientDescent.scala

@@ -12,6 +12,7 @@ object GradientDescent {
 
   /**
    * Run gradient descent in parallel using mini batches.
+   * Based on Matlab code written by John Duchi.
    *
    * @param data - Input data for SGD. RDD of form (label, [feature values]).
    * @param gradient - Gradient object that will be used to compute the gradient.

ml/src/main/scala/spark/ml/LogisticRegression.scala

@@ -6,6 +6,7 @@ import org.jblas.DoubleMatrix
 
 /**
  * Logistic Regression using Stochastic Gradient Descent.
+ * Based on Matlab code written by John Duchi.
  */
 class LogisticRegressionModel(
   val weights: DoubleMatrix,
@@ -80,9 +81,6 @@ class LogisticRegression(var stepSize: Double, var miniBatchFraction: Double, va
   }
 }
 
-/**
- * Helper classes to build a LogisticRegression object.
- */
 object LogisticRegression {
 
   def main(args: Array[String]) {