Py33 fixes

Hey @cabrera!

Nice work on porting python-memcached to Python 3!

I did a few more tweaks and now the tox tests (also excellent!) are passing for me:

```
$ tox
py26 develop-inst-nodeps: /Users/marca/dev/git-repos/python-memcached
py26 runtests: PYTHONHASHSEED='2442499963'
py26 runtests: commands[0] | nosetests
MemCached: MemCache: inet:memcached:11211: connection closed in readline().  Marking dead.
MemCached: MemCache: inet:memcached:11211 (dead until 1395722607): connection closed in readline().  Marking dead.
.
----------------------------------------------------------------------
Ran 1 test in 0.015s

OK
py27 develop-inst-nodeps: /Users/marca/dev/git-repos/python-memcached
py27 runtests: PYTHONHASHSEED='2442499963'
py27 runtests: commands[0] | nosetests
MemCached: MemCache: inet:memcached:11211: connection closed in readline().  Marking dead.
MemCached: MemCache: inet:memcached:11211 (dead until 1395722611): connection closed in readline().  Marking dead.
.
----------------------------------------------------------------------
Ran 1 test in 0.012s

OK
py33 develop-inst-nodeps: /Users/marca/dev/git-repos/python-memcached
py33 runtests: PYTHONHASHSEED='2442499963'
py33 runtests: commands[0] | nosetests
MemCached: MemCache: inet:memcached:11211: connection closed in readline().  Marking dead.
MemCached: MemCache: inet:memcached:11211 (dead until 1395722615): connection closed in readline().  Marking dead.
.
----------------------------------------------------------------------
Ran 1 test in 0.012s

OK
pypy develop-inst-nodeps: /Users/marca/dev/git-repos/python-memcached
pypy runtests: PYTHONHASHSEED='2442499963'
pypy runtests: commands[0] | nosetests
MemCached: MemCache: inet:memcached:11211: connection closed in readline().  Marking dead.
MemCached: MemCache: inet:memcached:11211 (dead until 1395722620): connection closed in readline().  Marking dead.
.
----------------------------------------------------------------------
Ran 1 test in 0.018s

OK
pep8 develop-inst-nodeps: /Users/marca/dev/git-repos/python-memcached
pep8 runtests: PYTHONHASHSEED='2442499963'
pep8 runtests: commands[0] | flake8
./memcache.py:1:1: H802  git commit title ('check_key: Auto-convert unicode keys to bytes for better Python 3 compat') should be under 50 chars
./memcache.py:64:80: E501 line too long (87 > 79 characters)
ERROR: InvocationError: '/Users/marca/dev/git-repos/python-memcached/.tox/pep8/bin/flake8'
___________________________________________________________________________________ summary ____________________________________________________________________________________
  py26: commands succeeded
  py27: commands succeeded
  py33: commands succeeded
  pypy: commands succeeded
ERROR:   pep8: commands failed
```

Hopefully you can merge my stuff into your branch and then @linsomniac will merge your PR (https://github.com/linsomniac/python-memcached/pull/26)!