Update Python required version to 2.7, and mention MLlib support

docs/python-programming-guide.md

@@ -52,7 +52,7 @@ In addition, PySpark fully supports interactive use---simply run `./bin/pyspark`
 
 # Installing and Configuring PySpark
 
-PySpark requires Python 2.6 or higher.
+PySpark requires Python 2.7 or higher.
 PySpark applications are executed using a standard CPython interpreter in order to support Python modules that use C extensions.
 We have not tested PySpark with Python 3 or with alternative Python interpreters, such as [PyPy](http://pypy.org/) or [Jython](http://www.jython.org/).
 
@@ -149,6 +149,12 @@ sc = SparkContext(conf = conf)
 [API documentation](api/pyspark/index.html) for PySpark is available as Epydoc.
 Many of the methods also contain [doctests](http://docs.python.org/2/library/doctest.html) that provide additional usage examples.
 
+# Libraries
+
+[MLlib](mllib-guide.html) is also available in PySpark. To use it, you'll need
+[NumPy](http://www.numpy.org) version 1.7 or newer. The [MLlib guide](mllib-guide.html) contains
+some example applications.
+
 # Where to Go from Here
 
 PySpark also includes several sample programs in the [`python/examples` folder](https://github.com/apache/incubator-spark/tree/master/python/examples).