Add Morfessor and Sklearn to Test Requirements in setup.py

[aptlin]

Description

1. testAddMorphemesToEmbeddings imports morfessor, but the module is not declared as a dependence for testing in setup.py. Will adding a try-except loop help?
2. Similarly, test_sklearn_integration imports sklearn, but it is not mentioned in setup.py.

Steps/Code/Corpus to Reproduce

python setup.py test

Expected Results

Clear installation.

Actual Results

======================================================================
ERROR: testAddMorphemesToEmbeddings (gensim.test.test_varembed_wrapper.TestVarembed)
Test add morphemes to Embeddings
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/nix-build-python3.5-gensim-2.1.0.drv-0/gensim-2.1.0/gensim/models/wrappers/varembed.py", line 68, in load_varembed_format
    import morfessor
ImportError: No module named 'morfessor'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/tmp/nix-build-python3.5-gensim-2.1.0.drv-0/gensim-2.1.0/gensim/test/test_varembed_wrapper.py", line 56, in testAddMorphemesToEmbeddings
    vectors=varembed_model_vector_file, morfessor_model=varembed_model_morfessor_file)
  File "/tmp/nix-build-python3.5-gensim-2.1.0.drv-0/gensim-2.1.0/gensim/models/wrappers/varembed.py", line 74, in load_varembed_format
    raise ImportError('Could not import morfessor.')
ImportError: Could not import morfessor.

======================================================================
ERROR: test_sklearn_integration (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_sklearn_integration
Traceback (most recent call last):
  File "/nix/store/ngfvnb22lh72z8prslmfdd2aiis5z08p-python3-3.5.3/lib/python3.5/unittest/loader.py", line 153, in loadTestsFromName
    module = __import__(module_name)
  File "/tmp/nix-build-python3.5-gensim-2.1.0.drv-0/gensim-2.1.0/gensim/test/test_sklearn_integration.py", line 9, in <module>
    from sklearn.pipeline import Pipeline
ImportError: No module named 'sklearn'

Versions

Linux-4.9.27-x86_64-with-glibc2.3.4
Python 3.5.3 (default, Jan 17 2017, 07:57:56)
[GCC 5.4.0]
NumPy 1.11.3
SciPy 0.18.1
gensim 2.1.0
FAST_VERSION 0

[tmylk]

After this change
d3db946
pip install gensim[test] installs them.

However the tests for sklearn and varembed/mofressor shouldn't run when they are not installed, same way as WMD tests. TODO: skip tests if sklearn or morfessor not installed.

[menshikh-iv]

All fixed, now you can run pip install .[test]; python setup.py test and tests will run correctly.