SPARK-1426: Make MLlib work with NumPy versions older than 1.7

Currently it requires NumPy 1.7 due to using the copyto method (http://docs.scipy.org/doc/numpy/reference/generated/numpy.copyto.html) for extracting data out of an array.
Replace it with a fallback

Author: Sandeep <sandeep@techaddict.me>

Closes #391 from techaddict/1426 and squashes the following commits:

d365962 [Sandeep] SPARK-1426: Make MLlib work with NumPy versions older than 1.7 Currently it requires NumPy 1.7 due to using the copyto method (http://docs.scipy.org/doc/numpy/reference/generated/numpy.copyto.html) for extracting data out of an array. Replace it with a fallback

(cherry picked from commit df360917990ad95dde3c8e016ec42507d1566355)
Signed-off-by: Matei Zaharia <matei@databricks.com>