Add python3.7 support

[menshikh-iv]

Just add python3.7 support

[menshikh-iv]

Fails on win produced by undetermined tests, this will be passed after some number of re-runs (but I'm tired to restart full build each time, appveyor still have no way to restart only one build job). So, I merge this (but we definitely need to do something with most-frequent-failing tests).

[piskvorky]

Fails on win produced by undetermined tests … definitely need to do something with most-frequent-failing tests.

@menshikh-iv which tests are these?

[menshikh-iv]

@piskvorky

• TestFastTextModel.test_cbow_hs_online

____________________ TestFastTextModel.test_cbow_hs_online _____________________
self = <gensim.test.test_fasttext.TestFastTextModel testMethod=test_cbow_hs_online>
    @unittest.skipIf(IS_WIN32, "avoid memory error with Appveyor x32")
    def test_cbow_hs_online(self):
        model = FT_gensim(
            sg=0, cbow_mean=1, alpha=0.05, window=2, hs=1, negative=0, min_count=3, iter=1, seed=42, workers=1
        )
>       self.online_sanity(model)
model      = <gensim.models.fasttext.FastText object at 0x7fb8e2470e80>
self       = <gensim.test.test_fasttext.TestFastTextModel testMethod=test_cbow_hs_online>
gensim/test/test_fasttext.py:707: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
gensim/test/test_fasttext.py:690: in online_sanity
    self.assertLess(0., sim)
E   AssertionError: 0.0 not less than -0.96153259

• TestWord2VecModel.test_cbow_hs_fromfile

___________________ TestWord2VecModel.test_cbow_hs_fromfile ____________________
self = <gensim.test.test_word2vec.TestWord2VecModel testMethod=test_cbow_hs_fromfile>
    @unittest.skipIf(os.name == 'nt' and six.PY2, "CythonLineSentence is not supported on Windows + Py27")
    def test_cbow_hs_fromfile(self):
        model = word2vec.Word2Vec(
            sg=0, cbow_mean=1, alpha=0.05, window=8, hs=1, negative=0,
            min_count=5, iter=10, workers=2, batch_words=1000
        )
>       self.model_sanity(model, with_corpus_file=True)
model      = <gensim.models.word2vec.Word2Vec object at 0x7fb8ec18f9b0>
self       = <gensim.test.test_word2vec.TestWord2VecModel testMethod=test_cbow_hs_fromfile>
gensim/test/test_word2vec.py:687: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
gensim/test/test_word2vec.py:647: in model_sanity
    self.assertLess(t_rank, 50)
E   AssertionError: 66 not less than 50

• TestDoc2VecModel.testLoadOldModel

______________________ TestDoc2VecModel.testLoadOldModel ______________________
self = <gensim.test.test_doc2vec.TestDoc2VecModel testMethod=testLoadOldModel>
    def testLoadOldModel(self):
        """Test loading doc2vec models from previous version"""
    
        model_file = 'doc2vec_old'
        model = doc2vec.Doc2Vec.load(datapath(model_file))
        self.assertTrue(model.wv.vectors.shape == (3955, 100))
        self.assertTrue(len(model.wv.vocab) == 3955)
        self.assertTrue(len(model.wv.index2word) == 3955)
        self.assertIsNone(model.corpus_total_words)
        self.assertTrue(model.syn1neg.shape == (len(model.wv.vocab), model.vector_size))
        self.assertTrue(model.trainables.vectors_lockf.shape == (3955, ))
        self.assertTrue(model.vocabulary.cum_table.shape == (3955, ))
    
        self.assertTrue(model.docvecs.vectors_docs.shape == (300, 100))
        self.assertTrue(model.trainables.vectors_docs_lockf.shape == (300, ))
        self.assertTrue(model.docvecs.max_rawint == 299)
        self.assertTrue(model.docvecs.count == 300)
    
        self.model_sanity(model)
    
        # Model stored in multiple files
        model_file = 'doc2vec_old_sep'
        model = doc2vec.Doc2Vec.load(datapath(model_file))
        self.assertTrue(model.wv.vectors.shape == (3955, 100))
        self.assertTrue(len(model.wv.vocab) == 3955)
        self.assertTrue(len(model.wv.index2word) == 3955)
        self.assertIsNone(model.corpus_total_words)
        self.assertTrue(model.syn1neg.shape == (len(model.wv.vocab), model.vector_size))
        self.assertTrue(model.trainables.vectors_lockf.shape == (3955, ))
        self.assertTrue(model.vocabulary.cum_table.shape == (3955, ))
    
        self.assertTrue(model.docvecs.vectors_docs.shape == (300, 100))
        self.assertTrue(model.trainables.vectors_docs_lockf.shape == (300, ))
        self.assertTrue(model.docvecs.max_rawint == 299)
        self.assertTrue(model.docvecs.count == 300)
    
        self.model_sanity(model)
    
        # load really old model
        model_file = 'd2v-lee-v0.13.0'
        model = doc2vec.Doc2Vec.load(datapath(model_file))
>       self.model_sanity(model)
model      = <gensim.models.doc2vec.Doc2Vec object at 0x000000268F86FEF0>
model_file = 'd2v-lee-v0.13.0'
self       = <gensim.test.test_doc2vec.TestDoc2VecModel testMethod=testLoadOldModel>
c:\python36-x64\lib\site-packages\gensim\test\test_doc2vec.py:146: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
c:\python36-x64\lib\site-packages\gensim\test\test_doc2vec.py:357: in model_sanity
    self.assertLess(f_rank, 10)
E   AssertionError: 10 not less than 10