[SPARK-5012][MLLib][PySpark]Python API for Gaussian Mixture Model

Python API for the Gaussian Mixture Model clustering algorithm in MLLib.

Author: FlytxtRnD <meethu.mathew@flytxt.com>

Closes #4059 from FlytxtRnD/PythonGmmWrapper and squashes the following commits:

c973ab3 [FlytxtRnD] Merge branch 'PythonGmmWrapper', remote-tracking branch 'upstream/master' into PythonGmmWrapper
339b09c [FlytxtRnD] Added MultivariateGaussian namedtuple  and Arraybuffer in trainGaussianMixture
fa0a142 [FlytxtRnD] New line added
d5b36ab [FlytxtRnD] Changed argument names to lowercase
ac134f1 [FlytxtRnD] Merge branch 'PythonGmmWrapper' of https://github.com/FlytxtRnD/spark into PythonGmmWrapper
6671ea1 [FlytxtRnD] Added mllib/stat/distribution.py
3aee84b [FlytxtRnD] Fixed style issues
2e9f12a [FlytxtRnD] Added mllib/stat/distribution.py and fixed style issues
b22532c [FlytxtRnD] Merge branch 'PythonGmmWrapper', remote-tracking branch 'upstream/master' into PythonGmmWrapper
2e14d82 [FlytxtRnD] Incorporate MultivariateGaussian instances in GaussianMixtureModel
05767c7 [FlytxtRnD] Merge branch 'PythonGmmWrapper', remote-tracking branch 'upstream/master' into PythonGmmWrapper
3464d19 [FlytxtRnD] Merge branch 'PythonGmmWrapper', remote-tracking branch 'upstream/master' into PythonGmmWrapper
c1d4c71 [FlytxtRnD] Merge branch 'PythonGmmWrapper', remote-tracking branch 'origin/PythonGmmWrapper' into PythonGmmWrapper
426d130 [FlytxtRnD] Added random seed parameter
332bad1 [FlytxtRnD] Merge branch 'PythonGmmWrapper', remote-tracking branch 'upstream/master' into PythonGmmWrapper
f82750b [FlytxtRnD] Fixed style issues
5c83825 [FlytxtRnD] Split input file with space delimiter
fda60f3 [FlytxtRnD] Python API for Gaussian Mixture Model