This patch consists of the following changes:

* Splitting eventlet.greenio into base, py2 and py3 parts
  (eventlet.greenio should be exporing the same public objects). This
  change is motivated by the size and the number of conditions present
  in the current greenio code
* Connected to the first point: implementing almost completely new
  GreenPipe callable utilizing parts of old GreenPipe code but dropping
  _fileobject/SocketIO inheritance in favour of io.FileIO and making use
  of patched _pyio.open function which wraps raw file-like object in
  various readers and writers (they take care of the buffering,
  encoding/decoding etc.)
* Implementing (from scratch or updating existing versions)
  green versions of the following modules:

  * http.* (needed by Python 3's urllib)
  * selectors (Python >= 3.4, used in subprocess module)
  * urllib.* (needed by various tests and we were already exposing green
    urllib)

* Modifying some tests to make tests pass, which includes:

  * unicode/bytestring issues
  * modifying wsgi_test_conntimeout.py to not pass bufsize and close
    arguments to ExplodingSocketFile - on Python 3 it inherits from
    SocketIO, which doesn't deal with buffering at all as far as I can
    see

* Random cleaning up and reorganizing
* Requiring Python 3.x tests to pass for the whole build to pass

Known issues:

* code repetition
* naming inconsistencies
* possibly breaking some external code using private eventlet.greenio attributes

Closes https://github.com/eventlet/eventlet/issues/108

Affects https://github.com/eventlet/eventlet/issues/6 (I'd call it an
experimental support)

Should help for https://github.com/eventlet/eventlet/issues/145
Should help for https://github.com/eventlet/eventlet/issues/157

GreenPipe will most likely need to be rewritten for Python 3 but this'll
do for some cases

Closes #137
Closes #148

This includes changes to WSGI, websocket, bytes/str/unicode handling,
SSL, backdoor, greenio and tests.

Some comments and conditionals (PY2/PY3) were added for clarity

GH issues:

Closes #106
Closes #111
Closes #118
Closes #141

Incidentally should also close #135 (reopen if didn't)

cc #6

https://github.com/eventlet/eventlet/issues/122

After a long running job that highlighted a previous known issue with
Second Simultaneous Read issue I used http://mg.pov.lt/objgraph/ to print
out all the types and counts still referenced by the GC.

Before this patch I was seeing GreenSocket and _socketobject types been
referenced. Depending on how long I ran the test job for I saw more references
to these objects. After this patch I see no reference no matter how long I
run my test for.

https://github.com/eventlet/eventlet/issues/94

We have to defang the listener after removing it from the hub

Otherwise we never actaully remove it from the hub and get a return of the
second simultanous read.

This should fix this issue.

Turn off __builtin__ monkey patching by default

The reason is that eventlet.greenio.GreenPipe tries to
adapt an original file f, and performs the following check
isinstance(f, file) f is an original file object with file
is now our file method. This fails causing TypeError

nova-api exercises this

Fix up zmq to use the extended add signature

Having heard no problems relating eventlet and zmq,
I'm not going to dive in and drop random pataches against
it. If the 'Second simultaneous *er' crops up against
zmw then we at least now have the machinery to
address it.