[SPARK-4969][STREAMING][PYTHON] Add binaryRecords to streaming

In Spark 1.2 we added a `binaryRecords` input method for loading flat binary data. This format is useful for numerical array data, e.g. in scientific computing applications. This PR adds support for the same format in Streaming applications, where it is similarly useful, especially for streaming time series or sensor data.

Summary of additions
- adding `binaryRecordsStream` to Spark Streaming 
- exposing `binaryRecordsStream` in the new PySpark Streaming
- new unit tests in Scala and Python

This required adding an optional Hadoop configuration param to `fileStream` and `FileInputStream`, but was otherwise straightforward.

@tdas @davies
Maybe it's not an issue since we're using FixedLengthBinaryInputFormat, but even if it isn't we should have a comment explaining why it's correct or a defensive check that `getBytes` returns an array of the expected length.