Update setup.py for Python3 compatibility

make setuptools use 2to3 when installing under python3
Fix call to train_test_split in plot_latent_crf example. Scikit-learn's train_test_split changed its behaviour for nd samples in version 0.15.
Merge pull request #109 from bjanssen/master

Fix call to train_test_split in plot_latent_crf example.
Merge pull request #108 from tp199911/patch-1

Update setup.py for Python3 compatibility
fix subgradient batch bug and add a test
subgradient test: add another check
Merge pull request #111 from martinsch/subgradient_batch_fix

fix subgradient batch bug and add a test