Pip3 support

[Louis-T]

Hi,

I'm interested in this library which seems really good, but I'm currently using Python3, and I'm struggling to install lopq via pip3 (sudo pip3 install lopq).

The installation with pip3 seems to be fine, but it gives me the following error when trying to import lopq :

>>> import lopq
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.5/dist-packages/lopq/__init__.py", line 3, in <module>
    import model
ImportError: No module named 'model'

It works fine when installing it via pip, but then I can't import it in Python3.