Test writing unicode objects
Implement writing unicode as UTF-8 for local and jpipe back ends
whitespace
Access data to be written through the buffer interface

This allows us to avoid having a separate method for ctypes buffer
objects.  In fact, by accessing objects through the buffer interface we
can transparently write just about any byte-oriented data type.

The down side is that our writes may work where Python's standard file
object would raise a TypeError.
Fix handling of unicode strings in hdfs write function

Unicode strings need to be encoded using the system encoding before
being written. The code was instead trying to access them directy as a
python buffer, which would fail with a TypeError.
Encode unicode strings as utf-8 when writing through the C extension for HDFS

Previous implementation used the default system encoding.
Merge pull request #28 from ilveroluca/write_through_buffer

Access data to be written through the buffer interface