Remove pytest-catchlog from dependences.

We've been getting warnings about it having been merged into pytest
core, e.g:

    https://travis-ci.org/CCI-MOC/hil/jobs/341455006#L2725

This also bumps the minimum version for pytest in our setup.py, since
the change was made in 3.3.0:

* https://docs.pytest.org/en/latest/changelog.html#id56
* pytest-dev/pytest#2794

setup.py

@@ -92,8 +92,7 @@ def _get_readme():
                         ],
       extras_require={
           'tests': [
-                'pytest>=3.0.0,<4.0',
-                'pytest-catchlog>=1.2.2,<2.0',
+                'pytest>=3.3.0,<4.0',
                 'pytest-cov>2.0,<3.0',
                 'pytest-xdist>=1.14,<2.0',
                 'pycodestyle>=2.3.1',