add test dependencies to extras_require

Allows you to `pip install .[test]`

setup.py

@@ -18,6 +18,7 @@ def read_file(fname):
 
 needs_pytest = {'pytest', 'test', 'ptr'}.intersection(sys.argv)
 pytest_runner = ['pytest-runner'] if needs_pytest else []
+test_deps = ["mock", "pytest", "pytest-cov"]
 
 setup(
     name="luma.core",
@@ -34,11 +35,12 @@ def read_file(fname):
     packages=["luma.core", "luma.core.legacy"],
     install_requires=["pillow>=4.0.0", "smbus2", "spidev", "RPi.GPIO"],
     setup_requires=pytest_runner,
-    tests_require=["mock", "pytest", "pytest-cov", "python-coveralls"],
+    tests_require=test_deps,
     extras_require={
         'docs': [
             'sphinx >= 1.5.1'
-        ]
+        ],
+        'test': test_deps
     },
     zip_safe=False,
     classifiers=[