Add compatibility with python 3

[SleepProgger]

First of all: thanks for this project, it works really nice.

Python3 support would be nice. Especially because the debian repos only have the python3-caffe package but not the one for python 2.

I got it running under py3 (and could send an PR if requested).

The main problems are:

• Some missing brackets at print statements.
• PyQt4 under python 3 doesn't have QString (or it least it looks like it), but that can be replaced by simply using strings with something like:

  try:
  from PyQt4.QtCore import QString
  except ImportError:
  QString = str

  should work.

• Python 3 always returns a float as a result of divisions by / (not //) which lead to some problems with sklearn/numpy. Downgrading numpy to version 1.11.0 ike described here solved that problem.

[Epochilili]

PR , I also want to run in python3 environment.Thank you.