Remove the getStageInfo() method from SparkContext.

This method exposes the Stage objects, which are
private to Spark and should not be exposed to the
user.

This method was added in https://github.com/apache/spark/commit/01d77f329f5878b7c8672bbdc1859f3ca95d759d; ccing @squito here in case there's a good reason to keep this!

Author: Kay Ousterhout <kayousterhout@gmail.com>

Closes #308 from kayousterhout/remove_public_method and squashes the following commits:

2e2f009 [Kay Ousterhout] Remove the getStageInfo() method from SparkContext.
[SPARK-1371] fix computePreferredLocations signature to not depend on underlying implementation

Change to Map and Set - not mutable HashMap and HashSet

Author: Mridul Muralidharan <mridulm80@apache.org>

Closes #302 from mridulm/master and squashes the following commits:

df747af [Mridul Muralidharan] Address review comments
17e2907 [Mridul Muralidharan] fix computePreferredLocations signature to not depend on underlying implementation
Fix for PR #195 for Java 6

Use Java 6's recommended equivalent of Java 7's Logger.getGlobal() to retain Java 6 compatibility. See PR #195

Author: Sean Owen <sowen@cloudera.com>

Closes #334 from srowen/FixPR195ForJava6 and squashes the following commits:

f92fbd3 [Sean Owen] Use Java 6's recommended equivalent of Java 7's Logger.getGlobal() to retain Java 6 compatibility
SPARK-1421. Make MLlib work on Python 2.6

The reason it wasn't working was passing a bytearray to stream.write(), which is not supported in Python 2.6 but is in 2.7. (This array came from NumPy when we converted data to send it over to Java). Now we just convert those bytearrays to strings of bytes, which preserves nonprintable characters as well.

Author: Matei Zaharia <matei@databricks.com>

Closes #335 from mateiz/mllib-python-2.6 and squashes the following commits:

f26c59f [Matei Zaharia] Update docs to no longer say we need Python 2.7
a84d6af [Matei Zaharia] SPARK-1421. Make MLlib work on Python 2.6
merging master