python3 support and auto autodetect so file

[sword865]

add python3 support and auto autodetect so file

[PorkShoulderHolder]

when i try to manually compile this via
g++ --std=c++11 *.cpp -shared -o libmf.so
and then run
python mf_tests.py I get

dlsym(RTLD_DEFAULT, fit_interface): symbol not found
FAILED
testing predict method
(1000, 2)
OK
testing cross validation
FAILED
dlsym(RTLD_DEFAULT, cross_valid_interface): symbol not found

similarly if i merge with the current master and compile and use the new test script i get

➜  python-libmf git:(sword865-master) ✗ python -m tests.mf_tests
Traceback (most recent call last):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/Users/samuelroyston/python-libmf-workdir/python-libmf/tests/mf_tests.py", line 6, in <module>
    class TestMF(TestCase):
  File "/Users/samuelroyston/python-libmf-workdir/python-libmf/tests/mf_tests.py", line 9, in TestMF
    mf_engine.mf_fit(test_data)
  File "libmf/mf.py", line 139, in mf_fit
    mf.fit_interface.restype = ctypes.POINTER(MFModel)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 378, in __getattr__
    func = self.__getitem__(name)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 383, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(RTLD_DEFAULT, fit_interface): symbol not found

if you fix this and ensure the builds via setup.py also work I'll merge your changes. We will need more support for other platforms in the future so the lib_path file might make sense.