MLLIB-24: url of "Collaborative Filtering for Implicit Feedback Datasets" in ALS is invalid now

url of "Collaborative Filtering for Implicit Feedback Datasets"  is invalid now. A new url is provided. http://research.yahoo.com/files/HuKorenVolinsky-ICDM08.pdf

Author: Chen Chao <crazyjvm@gmail.com>

Closes #619 from CrazyJvm/master and squashes the following commits:

a0b54e4 [Chen Chao] change url to IEEE
9e0e9f0 [Chen Chao] correct spell mistale
fcfab5d [Chen Chao] wrap line to to fit within 100 chars
590d56e [Chen Chao] url error

mllib/src/main/scala/org/apache/spark/mllib/recommendation/ALS.scala

@@ -81,7 +81,7 @@ case class Rating(val user: Int, val product: Int, val rating: Double)
  *
  * For implicit preference data, the algorithm used is based on
  * "Collaborative Filtering for Implicit Feedback Datasets", available at
- * [[http://research.yahoo.com/pub/2433]], adapted for the blocked approach used here.
+ * [[http://dx.doi.org/10.1109/ICDM.2008.22]], adapted for the blocked approach used here.
  *
  * Essentially instead of finding the low-rank approximations to the rating matrix `R`,
  * this finds the approximations for a preference matrix `P` where the elements of `P` are 1 if