Induce spilling in ExternalAppendOnlyMapSuite
Add number of bytes spilled to Web UI
Add Naive Bayes to Python MLlib, and some API fixes

- Added a Python wrapper for Naive Bayes
- Updated the Scala Naive Bayes to match the style of our other
  algorithms better and in particular make it easier to call from Java
  (added builder pattern, removed default value in train method)
- Updated Python MLlib functions to not require a SparkContext; we can
  get that from the RDD the user gives
- Added a toString method in LabeledPoint
- Made the Python MLlib tests run as part of run-tests as well (before
  they could only be run individually through each file)
Update some Python MLlib parameters to use camelCase, and tweak docs

We've used camel case in other Spark methods so it felt reasonable to
keep using it here and make the code match Scala/Java as much as
possible. Note that parameter names matter in Python because it allows
passing optional parameters by name.
Added Java unit test, data, and main method for Naive Bayes

Also fixes mains of a few other algorithms to print the final model
Log Python exceptions to stderr as well

This helps in case the exception happened while serializing a record to
be sent to Java, leaving the stream to Java in an inconsistent state
where PythonRDD won't be able to read the error.
Update Python required version to 2.7, and mention MLlib support
Fix Scala version in docs (it was printed as 2.1)
Get rid of spill map in SparkEnv
Enable external sorting by default
Report bytes spilled for both memory and disk on Web UI
Improvements to external sorting

1. Adds the option of compressing outputs.
2. Adds batching to the serialization to prevent OOM on the read side.
3. Slight renaming of config options.
4. Use Spark's buffer size for reads in addition to writes.
Changing option wording per discussion with Andrew
Added unpersisting and modified testsuite to better test out metadata cleaning.
Merge pull request #410 from rxin/scaladoc1

Updated JavaStreamingContext to make scaladoc compile.

`sbt/sbt doc` used to fail. This fixed it.
Improved file input stream further.
Merge remote-tracking branch 'apache/master' into filestream-fix
Fix for Kryo Serializer
Add default value for HadoopRDD's `cloneRecords` constructor arg, to maintain backwards compatibility.
Merge pull request #411 from tdas/filestream-fix

Improved logic of finding new files in FileInputDStream

Earlier, if HDFS has a hiccup and reports a existence of a new file (mod time T sec) at time T + 1 sec, then fileStream could have missed that file. With this change, it should be able to find files that are delayed by up to <batch size> seconds. That is, even if file is reported at T + <batch time> sec, file stream should be able to catch it.

The new logic, at a high level, is as follows. It keeps track of the new files it found in the previous interval and mod time of the oldest of those files (lets call it X). Then in the current interval, it will ignore those files that were seen in the previous interval and those which have mod time older than X. So if a new file gets reported by HDFS that in the current interval, but has mod time in the previous interval, it will be considered. However, if the mod time earlier than the previous interval (that is, earlier than X), they will be ignored. This is the current limitation, and future version would improve this behavior further.

Also reduced line lengths in DStream to <=100 chars.