TST/CLN: remove np.assert_equal
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`

Not to use `np.testing.assert_equal`, as `assert_numpy_array_equal` is more strict to check dtypes.

I think we need to add something to maybe the lint.sh script to prevent anything np.testing from slipping back in

maybe a recursive grep would work?
 I think we could do something like this; if these are fixed (then just test if this grep outputs any lines, if so fail the lint.sh)

```
[Mon May 23 19:33:26 ~/pandas]$ grep -r --include '*.py' --exclude nosetester.py 'from numpy.testing import' pandas 
pandas/computation/tests/test_eval.py:from numpy.testing import assert_allclose
pandas/io/tests/json/test_ujson.py:from numpy.testing import (assert_array_almost_equal_nulp,
pandas/stats/tests/test_var.py:from numpy.testing import run_module_suite, TestCase
pandas/tests/test_graphics.py:from numpy.testing import assert_allclose
pandas/tseries/tests/test_converter.py:from numpy.testing import assert_almost_equal as np_assert_almost_equal
pandas/tseries/tests/test_timedeltas.py:from numpy.testing import assert_allclose
```
 thanks @sinhrks nice cleanup
