Python 3.3+ support

All tests are passing on Python 2.7

On Python3.3, 3.4, two tests are still failing:
```
======================================================================
FAIL: test_username_preceded_japanese (__main__.TWPTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "ttp/tests.py", line 445, in test_username_preceded_japanese
    self.assertEqual(result.html, 'あ<a href="https://twitter.com/username">@username</a>')
AssertionError: 'あ@username' != 'あ<a href="https://twitter.com/username">@username</a>'
- あ@username
+ あ<a href="https://twitter.com/username">@username</a>


======================================================================
FAIL: test_username_surrounded_japanese (__main__.TWPTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "ttp/tests.py", line 455, in test_username_surrounded_japanese
    self.assertEqual(result.html, 'あ<a href="https://twitter.com/username">@username</a>の')
AssertionError: 'あ@usernameの' != 'あ<a href="https://twitter.com/username">@username</a>の'
- あ@usernameの
+ あ<a href="https://twitter.com/username">@username</a>の


----------------------------------------------------------------------
Ran 100 tests in 0.035s

FAILED (failures=2)
```
Trying to figure out how to fix those.

On 3.2 more tests are failing, but I'm not sure if 3.2 support is critical or not.

Ref #4