Clarify comment.
Merge pull request #199 from adonoho/use-bytearray-buffer

Reduce memory usage by writing directly into byte array buffer.
Gentlefolk,

The whole point of using a `bytearray` as opposed to concatenating reads of `bytes` was to reduce memory usage. This pull request now takes that strategy to its logical conclusion by writing the balance of the chunk directly into the `bytearray`. This saves the creation of a temporary `bytes` array, up to 8KiB in size.

It does this by creating a `memoryview` of the `bytearray`. While this is still an allocation, the `memoryview`s are much smaller and are, presumably, reclaimed faster.

This patch has been running for over 24 hours and has processed over 4 MTw under Python v3.3.3 on OS X 10.8.5. It has also been run for about 10 minutes on Python v2.7.6 on a similar machine. `memoryview` does not appear to have been backported to Python v2.6.*. Hence, this pull request is incompatible with that platform.

Anon,
Andrew

P.S. The changes in this pull request are larger than strictly necessary for adding this functionality. I chose to improve the naming of my variables and move some of them closer to where they are used.
Version 1.13.0. Ends support for Python 2.6.
Restore Python 2.6 compatibility by restoring the old version of recv_chunk, only used for Py 2.6.
Version 1.13.1.