Enable support for Python 3

[liuchbryan]

When I do:

from pybo import solve_bayesopt

the following error occurs:

---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-d54e95bf7a31> in <module>()
     10 from data_loader import *
     11 from evaluator import *
---> 12 from pybo import solve_bayesopt

/Users/bryan.liu/anaconda/envs/Python3/lib/python3.5/site-packages/pybo/__init__.py in <module>()
      4 
      5 # pylint: disable=wildcard-import
----> 6 from .bayesopt import *
      7 
      8 from . import bayesopt

/Users/bryan.liu/anaconda/envs/Python3/lib/python3.5/site-packages/pybo/bayesopt.py in <module>()
     13 import functools
     14 import os.path
---> 15 import cPickle as pickle
     16 import collections
     17 

ImportError: No module named 'cPickle'

The error is not seen if I use a Python 2-based environment, which lead to my belief that this is due to the replacement of cPickle to a more general pickle from Python 3.

While I am happy to stick with Python 2 for the moment, it might be a good idea to extend support to Python 3 as well. I am happy to circle back once I am done with the main work involving this lovely library (though would appreciate if other who have more free time to spare to have a go at it!).

Thanks a lot!

[RokoMijic]

Python 3 would definitely be good.