Fix TypeError caused by use_annotations=True on Python 3.3

I've encountered following error when trying to create Injector with use_annotations=True on python 3.3
```
Traceback (most recent call last):
  File "/home/iley/work/cms/abt/testing.py", line 66, in setUp
    super(AbtTestMixin, self).setUp()
  File "/home/iley/work/cms/frogstar/testing/fixture.py", line 10, in setUp
    self.injector = Injector(self.modules, use_annotations=True)
  File "/home/iley/.virtualenvs/cms3k/lib/python3.3/site-packages/injector.py", line 549, in __init__
    self.binder.install(module)
  File "/home/iley/.virtualenvs/cms3k/lib/python3.3/site-packages/injector.py", line 305, in install
    instance = self.injector.create_object(module)
  File "/home/iley/.virtualenvs/cms3k/lib/python3.3/site-packages/injector.py", line 591, in create_object
    bindings = self._infer_injected_bindings(cls.__init__)
  File "/home/iley/.virtualenvs/cms3k/lib/python3.3/site-packages/injector.py", line 618, in _infer_injected_bindings
    spec = getfullargspec(callable)
  File "/usr/lib/python3.3/inspect.py", line 851, in getfullargspec
    raise TypeError('{!r} is not a Python function'.format(func))
TypeError: <slot wrapper '__init__' of 'object' objects> is not a Python function
```
Turns out in Python 3.3 `object.__init__` is some kind of built-in object and it cannot be inspected via `inspect.getfullargspec()`. So I added a workaround for such case.