Avoid python 3 complexity bug
Avoid python 3 complexity bug

In python 3, running the hook causes an error:
```
File "/home/tom/.virtualenvs/happi-frontend/lib/python3.4/site-packages/flake8/hooks.py", line 48, in git_hook
    if complexity > -1:
TypeError: unorderable types: NoneType() > int()
```
Work around this by providing an explicit default in our hook, so there will always be a number to compare to, not `None`.
isotoma/precog